Is this a red flag?

Absolutely 1000% a red flag.

Gay friends are worse than having a mental disorder or two in my opinion.

It's nothing but highly sexualized, high sex drive humans (men) who are more promiscuous on average seemingly than even straight men, encouraging her to be a degenerate slut with no boundaries.

And because it's MEN encouraging her to be a slut, it's a huge breath of fresh air and they run with it even harder than if their female slut friends encouraged it.

Gay guy friends are such a red flag, I cannot understate how utterly destructive gay friends are to a woman's purity, if she even has a shred of it left by the time her gay friends encourage her

Edit: I'm not claiming women are pure, but if your average western hoe is a 4/10 on the purity scale having occasional casual sex, gay friends can and will drop her to a 2/10 on it in a short time frame

You ask WHY women like having gay men as friends? You need to ask yourself, what KIND of women like having gay besties ....its always modern feminist type women, not traditional women.

Why do modern feminist women like having gay male besties? Because gay men hate women even more than modern feminist women hate themselves. Feminism is a self hatred cult. Modern feminists love men that treat them like shit, and the men that really treat them worse than any chad are gay men. The entire fashion industry is built on the simple dynamic of acidic gay men treating straight women like human garbadge and telling them what they really want to hear - that they are too old, too fat, too unstylish and just basically trash and worthless. The rejection of a gay man is built in - and what these women really want is rejection.

If a girl has lots of gay friends, there’s a high chance that she isn’t straight either. You’re dealing with someone who’s probably lesbian or bisexual.

Not necessarily a red flag. It has to be looked at in context.
And ask yourself if you'd rather a girl have a bunch of straight male friends than gay male friends.

Girls instincts are largely based on hunter gatherer times, I think they're modelling staying attached to a (non-sexual) parent or important figure while sleeping with other people until an external force (pregnancy) causes them to attach to that person long term.

Thing is...this is a not-unusual pattern or behavior around puberty.

Puberty is a process that takes place for several years. Most girls finish puberty by age 14. Most boys finish puberty by age 15 or 16.

And obviously in modern times this is waaaaaaaaaaay earlier than people start having kids of their own, so they're like...in this pattern for a decade longer than usual? They're sort of stuck there because that external force (pregnancy) doesn't come along and push them into a long term choice like it did in the environment this behavior evolved in.

I don't think there's anything wrong with these girls as "plates", the issue is that to long term to bond they need extreme external pressure - that largely doesn't exist any more. Pressure from being pregnant, social pressure from the group around them (nearly every society pressures a pregnant woman to settle down for obvious reasons), pressure from her parents to move past being a child, etc. They girls can sleep around all the time but there's a complete lack of bonding in the way that they do it.

My 2 cents at least.

edit: On review I realized you said "multiple gay friends" and that's not really what I'm talking about...I'm talking about when she's overly attached to exactly 1 gay guy friend and everyone would think they're dating if he didn't mention that he's gay every 5 minutes.

Women with multiple gay friends is the similar to their desire to collect beta males non-sexually, their instincts are to try to have people around who are useful to them without the sex or romance drama.