It's interesting that she messaged you privately. She doesn't want one of the other 2, one of whom must be the Queen Bee, to know !
I was going to say this too. She thanked the others in the group chat but thanked you separately/privately....in my experience of women like this, that is because she can't look too friendly or nice towards you in front of them, which is because she joins them bitching about you, and putting you in the role of the barely tolerated group member.
They sound like a queen bee type and her two arse lickers. What a sad group dynamic. What an undesirable group dynamic (and sort of people).
I don't know why they still invited you to a few things .... To make themselves look/feel like nice people (when they're not). To have fodder/material to bitch about you and be derogatory about. Some people bond that way.
The not offering to give you a lift, even though they got there together, and then sneering at you not drinking because you couldn't afford an £80 taxi ......
These people are not friend material.
As a poster said, I bet if any of them get dumped/their relationships breaks down, they'll be all over you.
I also bet the queen bee and one of the others turn on the remains one when you've bowed out as the "let's bond over marginalising & ridiculing her" one.