The eighth grade girl told psychologist Ryan DeLapp that a friend only interacted with her when she wanted help with an assignment.

“This person would sit next to her in class but wouldn’t sit with her at lunch,” said DeLapp, director of the REACH program at the Ross Center in New York City. “She felt used, but it took several months for her to create distance because she worried that the girl would call her mean.”

As a school counselor, I know that parents are often mystified by kids’ social dynamics, which makes sense since those relationships are complex.

You can’t choose your children’s friends, but here’s how you can help them manage five frustrating friendship pitfalls.

Pitfall No. 1: Your child doesn’t want to ‘share’ a friend

How you can help: Start from a place of empathy, said psychologist Eileen Kennedy-Moore, coauthor of “Growing Friendships” and “Growing Feelings.”

“Say, ‘It’s understandable that you want your friend to yourself,’ then explain that being an octopus friend will backfire. If they squeeze too tightly, the friend will want to get away.”

Encourage your children to befriend their friend’s friend. If they resist, point out that if their friend likes the person, this companion probably has some redeeming qualities.

“Or stop playing tug of war and expand the triangle,” Kennedy-Moore added. “When you bring a fourth or fifth friend into the group, you lower the tension.”

Pitfall No. 2: A friendship is confusing or painful

How you can help: Ask them, ” ‘What do you think are the qualities of a friend, an acquaintance and a stranger?’ ” DeLapp said. Once you understand what they expect from a friend, say, ” ‘Based on what you just said, how would you categorize this friendship?’ “

Your child may realize that a friend is only an acquaintance. If that’s disappointing, help your child process the emotion. Ask, ” ‘How does it feel to say that what you want and what it really is are not matching up? What do they have to do to demonstrate to you that you’re their friend?’ ” DeLapp said. “The idea is to help them understand that (true) friendships are bidirectional.”

Share the concept of a “hot and cold” friend, too. “Sometimes they’re a lot of fun, and sometimes they’re definitely not,” Kennedy-Moore said. “When they’re running hot, say, ‘Great, enjoy them.’ When they’re running cold, they have a couple of options. One is to say, ‘This isn’t fun for me,’ and see if the other kid changes direction. Or they can use those good ‘I’ statements — ‘I don’t like it when you call me that.’ “

If a friendship is truly unhealthy, “frame the conflict as being within your own kid rather than between you and your child,” said psychologist Lisa Damour, author of “The Emotional Lives of Teenagers: Raising Connected, Capable, and Compassionate Adolescents.” Otherwise, they might “dig in their heels, as opposed to reflecting on why they’re pursuing a painful interaction.”

Help them reflect by saying, ” ‘Clearly, part of you wants to hang out with that classmate, but another part of you knows that every time you do, you walk away feeling lousy. Help me understand this,’ ” Damour said.

At the same time, “recognize how much children grow and change, and that a child who may be unkind at one point can readily turn into an incredibly warm and decent classmate,” she added.

Pitfall No. 3: Your children want to be part of a group that rejects them

How parents can help: A seventh grade girl told Damour that she couldn’t understand why the girls in a clique would hang out with her individually but wouldn’t invite her to sit with them at lunch. Damour shared a metaphor that can “help kids make better sense of data and move forward when they get mixed messages.”

She explained that kids’ friendships are like chemical compounds, with each child being an atom who makes bonds with other atoms. “Once kids are in compounds, they’re happy and won’t risk destabilizing that compound.” Damour told the girl she had two options — “Find other free-floating atoms or look for a compound open to new atoms.”

You can’t talk your children out of wanting to be part of a group, but you can try to understand their motivation, said Jennifer Fink, author of “Building Boys: Raising Great Guys in a World That Misunderstands Males.” For instance, “boys’ social world tends to be very hierarchical,” she said. “Everyone knows who the top dog is, and some kids try to get some of that power and frankly protection that comes from being part of that circle.”

“The hardest thing for parents is realizing we can’t solve this for our kids or make them stop caring,” Fink added. “But we can make observations like, ‘(Those boys) didn’t seem too interested when you were talking.’ ”

Pitfall No. 4: Your child can’t let go of a grudge

How parents can help: Two fifth grade girls came to my counseling office for help resolving a conflict. “When did it start?” I asked them. “Five years ago,” one replied.

Five years is a long time to nurse a grudge.

“We don’t want kids collecting grievances like beads on a string,” Kennedy-Moore noted. “Learning how to get past these friendship rough spots is crucial for learning how to have strong relationships.”

If your child fixates on something petty, play “the maybe game,” she added. Ask, ” ‘What are some possible reasons your friend did this other than deliberate meanness?’ “

She shares forgiveness guidelines with kids: “If it only happened once and is unlikely to happen again, let it go. If a friend is genuinely sorry, let it go. If it was an accident or a misunderstanding, let it go. If it happened more than a month ago, let it go.”

Pitfall No. 5: Your child frequently fights with friends

How parents can help: If your children are triggered, ask them what the incident means and why it’s happening. “They may be uncomfortable in a dynamic, but that doesn’t mean someone is mistreating them,” Kennedy-Moore said. “Change the thought, change the feeling.” That can make them less reactive.

Then ask, ” ‘What can you do that’s most likely to get the kind of response you want?’ ” Kennedy-Moore said. The best solution might simply be giving one another space. As she noted, “Research says that kids are more likely to solve disagreements by separating for a bit and then coming back together and just being nice to one another.”

Give them time for self-directed play so they can practice resolving conflict, added Peter Gray, a psychology professor at Boston College and author of “Free to Learn: Why Unleashing the Instinct to Play Will Make Our Children Happier, More Self-Reliant, and Better Students for Life.”

That’s how kids “learn to deal with conflict of all sorts — disruptions, disagreements, minor bullying,” Gray said. “We spend too much time protecting kids from conflict and not enough time letting them play freely with other kids, which is how they learn how to solve their own problems.”

Friendship is one of the few areas where kids have autonomy, so unless your children are in danger, give them a lot of leeway to pick their friends and their battles. “It’s tempting to leap in like a mother lioness and think, ‘I need to protect my child from that awful kid,’ ” Kennedy-Moore said, “but the other kid is a child, too.”

“Parents need to see their child’s discomfort as informational, not a sign there’s something really wrong,” Damour added. “Our emotions are our navigational system, and tuning in to how we feel when we’re with the different people in our lives gives us important feedback about who we may want to spend more or less time with.”

Phyllis L. Fagell, a licensed clinical professional counselor in Bethesda, Maryland, is the author of “Middle School Matters” and the forthcoming “Middle School Superpowers,” the school counselor at Sheridan School in Washington, DC, and a therapist at the Chrysalis Group. She tweets @pfagell and blogs at phyllisfagell.com.