Well basically the archetypical Straight Girl Social Group in my experience (and bear in mind I'm Jane Goodalling this shit) is composed of people socialised to be neurotic and emotionally needy. It's also a complex social environment with many unwritten rules and Rituals you are expected to perform, many of which revolve around providing one another with emotional validation.
E.g. if your girl friend says you look hot, occasionally you can just take the compliment, but mostly you are supposed to find something about your own appearance to criticise, and then tell her that she is flawless. And then she does that back to you, or you all stand in a group saying to each other, "I'm fat, you look amazing."
You have to very carefully monitor her moods towards the people in her life. You certainly can't have independent friendships or even acquaintances with the people your girl friends are dating (this is why it's often bad form to start dating someone that's related to or already friends with one of your friends) - the way it goes is that if she says he's awesome, you agree with her (to her face, anyway, you can definitely criticise him behind her back). However if she breaks up with him acrimoniously, you immediately always hated the guy and should tell her how much he never deserved her. You can also do this if she's probably gonna/ should break up with him, but BE WARY! If she complains about him but her relationship is stable, you're supposed to validate her complaints but not add to them. She's allowed to call her husband a deadbeat, but you aren't, unless you are, in which case it's obligatory. Got it?
Your lives with each other are very guess culture. You have to know which things you're meant to Show Up For (each friend group will have slightly different rules about this) and be aware that if you turn down such an invitation, she will make a big show of accepting your excuse as valid to your face, then turn around and immediately chat shit about you for abandoning her or quietly mope that you don't like her. You mustn't let your friend humiliate herself by double texting you and as such you're going to need to learn how long of a delay is going to convince her that you secretly hate her.
Everybody is so used to performing niceness to everyone's faces all the time that nobody has any idea whether any of the other girls actually like them. So to make each other feel better you'll have to do more performative validation, which will just make it worse.
Guy who thinks it's gay to text you more than once a day and is so emotionally repressed that if he says anything emotional he definitely means if is kind of relaxing, under the circumstances.