Speaking to a class of 18- and 19-year-old college students Wednesday, I asked if anyone had been in a toxic friendship. About half the students raised their hands.

They could not be themselves around these friends, some said. “I felt like I was stepping out of my authenticity to be with her,” one woman recounted of a friend she no longer speaks to.

They also pointed to deception and bullying: These toxic friends would make up lies or spread gossip, the students said, or were mean to their other friends. Some students said they broke things off directly; others severed the friendship by moving away for college and ignoring their calls.

None of them had read Natalie Beach’s opus about her friendship and falling out with Instagram influencer Caroline Calloway, which was published Tuesday on New York magazine’s the Cut and quickly went viral, but many had fallen into friendships that, similarly, started out blissful and ended up being destructive. What prompts someone to get sucked into a bad friendship? I asked the students. They blamed youthful insecurity, promises of certain perks (like trips to vacation homes), or someone’s uncanny ability to relate to them (which they later learned was made up).

There is something about forming female friendships in your teens and early 20s that can be intoxicating: You are trying to navigate the wilds of high school or college when someone comes along who seems to glide effortlessly through it, or appears just as lost as you are. You band together out of some combination of proximity, shared experiences and kismet, hoping that together, you can make sense out of the world around you and, of course, have a ton of fun. These kinds of friendships can be short-lived or lifelong. The best ones are healthy and mutually beneficial. But sometimes they are not.

As I read Beach’s story and Calloway’s responses on Instagram this week, I recalled a former roommate who stole from me. When I confronted her about it, she denied it. We never reached Beach and Calloway levels of dysfunction, but I was reminded of how easy it can be to fall into a bad friendship, especially when you are young, and how hard it can be to cut ties.

The essay prompted many readers to share the variations they experienced. A 34-year-old woman in Manila tweeted about how it took her 20 years to extricate herself from a friendship with a woman who was a habitual liar. When I called and asked how she knew it was time to end the relationship, she pointed to her other, thriving friendships. “I realized what a healthy friendship should be like,” she said. This woman met her toxic friend at a time when she was insecure, she said, and that “the little morsel of attention” this friend gave her was enough to draw her in.

Similarly, Calloway and Beach’s story seems to be borne of self-esteem issues and promise of access to a different kind of life. Beach met Calloway in a writing class at New York University. “All I saw was the beginning of something extraordinary,” Beach wrote of the start of her friendship with “the most confident girl I’d ever known.” To Beach’s telling, it was a mutual obsession: Beach grew up in New Haven, Conn., and Calloway was fixated on Yale after being rejected from the university, Beach writes. Calloway dished out compliments, telling Beach she was beautiful and a genius. They went to plays and clubs and fancy meals together. Calloway, who is wealthy, had a lifestyle that Beach, who is of modest upbringing, found enticing. “Soon I was broke but didn’t care,” Beach wrote. “I was now part of her life, a conspirator and confidante.”

Things started going downhill when Calloway began racking up Instagram followers; her following now hovers around 800,000. Beach wrote about how, on a trip together in Sicily, she would take photos of Calloway and help her write captions for the platform, all the while feeling secondary to Calloway’s relationship with Instagram. “I should have been having the time of my life in paradise,” Beach wrote, “but Caroline had a way of making me feel small, as if I had folded myself up like a travel toothbrush so she could take me along for the trip.”

When I asked one of the students if social media was making friendship harder, she said yes — because it is so easy to see where people are and who they are with, and that much more obvious when your crew is hanging out without you. But Beach and Calloway’s story highlights the toxic relationship many people have with social media, especially those who rely on it for their income. There is a point where living extremely online damages real-world relationships, and if you have grown up online, that tipping point might be hard to locate.

Beach goes on to become indebted to Calloway and, in a sense, becomes her maid to work off that debt. She could have parted ways once the tab was settled, but they continued to work together, co-writing a book proposal and later crashing on a draft of that book together. (Calloway ended up not finishing it and, according to the Cut essay, is working on a resolution with the publisher.) “She was constantly calling me her best friend and work wife, telling me she loved me,” Beach wrote. “I thought we were in this together.” Eventually that trust broke down as Calloway left Beach hanging on a night of “adventuring” in Amsterdam, and Beach realized that Calloway was dealing with bigger problems than Beach could help solve.

Beach and Calloway were in far deeper than the students I spoke with. I was impressed that, at only 18 and 19, they seemed to know where the boundaries of a healthy friendship lie: That obviously everyone deals with difficult things, and that friends can help talk those through and be supportive, but someone else’s problems are not a friend’s responsibility to solve or carry as their own. They seemed to grasp that, on balance, a friendship should leave you with more positive feelings than negative ones. And that arrangements where one person is the permanent supporting actor rarely feel good for long; both people in a friendship should get to take turns playing the starring role.