Although it has been a long time ago, I don't recall knowing any teenage girls as venomous as you describe. Not saying they aren't out there, but let's hope they are the exception and not the rule. Maybe I was just lucky.

This is one of those discussions even l'm not stupid enough to get involved in. ☺

Forget everything you think you know about women and girls and I will give you one hard fact. Women are smarter than men. Just let that sink in.

I don’t have an explanation for the way teenagers treat each other; but I’m sorry your daughter (and you) had to go through it.

Incel warning

Just kidding, teens in general I have found to be terrible.

There are few more toxic creatures on earth than teenage girls (though some start earlier). They will nasty you to death. Unfortunately, some don't grow out of it. As others have said, some of my biggest problems on the job were other women. It's particularly galling because we all claimed to be feminists and all about 'sisterhood'. And then the claws came out.

Your problem is you used teenage girls... that is like saying the most Idiotic, ignorant humans beings are teenage boys. Teens are not and never will be a Final Product of anything!!! Now, when I was in the Military, member of an Admiral Staff. We were briefed by American Intelligence experts, in case we ever encounter "terrorism while traveling overseas". What to look for, how to react, weak spots to exploit, etc, etc, etc. Object of the game is stay alive. We were told... "the worst terrorist" you can encounter... always going to be a woman. They play by a different set of rules and they have the tendency of taking on you just because you are a male. Because unlike men, women been done wrong by men and will hate men more easily than the other way around. There is no "machismo" on them so if they have to shot you in back, no problem... a male will like to look at you eye to eye... will like for you to find out who did it... there is none on that on the female. As children we are taught "chivalry" stories and games. At least most of us are taught one on one combat is the only "victory" you can achieve on your own. So females make perfect suicide bombers because they are brainwashed into following orders and that is as far in the "leadership" pole they can get. Men... think on surviving to be a leader as they dreamed since child... females are a different animal... wired different... taught different rules. We need male and female spies. There is a "sucker" born every minute! Example: "When a female know you are married or have a girlfriend. They will still have sex with you, but... They will leave behind a cheap hearing or her underwear in a place your wife or girlfriend will find it... In the kitchen, in the car, etc. Men do not leave behind any proof that they were there... don't want to get the cheating woman in trouble. Females will want you to get in trouble so they will leave you a "surprise" for the mrs or gf to find. Different animals but a woman in love will sell a nation as easy as a man will.

Parenting teenagers can be difficult. I do know, and I see it every day, that girls tend to be more socially nasty even when young. Boys tend to get more physical. I am talking three year olds. I don't know why. It would be good to figure that out.

Girls have become very mean lately. I agree. Look at the shows targeted to teenage girls! Instead of lifting each other up, they knock each other down.

Social media has made things worse for everyone, not just teenagers. I have friends who now home school their daughters because of bullying. One changed schools to get away from the bullying. My niece was bullied so badly by other girls she attempted suicide. She didn’t succeed and is now 22 and thriving. It was bad when I was a teenager, but there are more platforms available now for deliberate humiliation. So, yeah it’s gotten worse!

Back when we were all still walking across Pangea, uphill-both ways, to get to school, I don't recollect teenage girls being nearly as vicious as they seem to be now. Sure, there were rumors, innuendo, snide remarks, and even the occasional fistfight, but nothing like what is happening now.
The level of cruelty seems to have risen exponentially with the advent of social media.
Hope your someone gets to feeling better soon. Luckily, being a teenager isn't forever. Best to learn to be thick-skinned now though. The real world isn't any nicer.

I had some wonderful supportive friends as a teenager. They helped me through my toxic home life enormously.

Really? Because in my personal experience, men who are really immature boys stuck in the body of a man are actually the most cruel and heartless species with ice running through their veins....

Stop watching too much anime.