We can’t tell if our friend is fake or not

Me and one of my closest and longest friends (T, I’ve known her since I was 3) have been getting weird vibes from one of our newer friends (B, known for about 2-3 years) one of our other friends (Y, T and I’s best friend for 5 years) introduced B into our group a few years ago after having a falling out with her previous friends which obviously divided our friend group up a bit, then B’s friend(G) from said previous friend group was sort of ostracised so B brought them into our group as well.
The problem is that B is always blowing hot and cold with our group now, I’m closest with T now and we miss spending time with Y, Y and B are always together and Y acts differently when they’re around each other.
Most recently (last week) I was speaking to everyone B, Y, T and another friend who isn’t involved about how myself, Y and G finish our maths course this year (G wasn’t there) and I was wondering if I could do an epq in one year, B then says “wow, way to make me feel crap”, later on that day I overheard B and Y talking about T, saying that like T but feel like they have babysit and entertain when she’s around, I do kind of get it because she can be very emotional and if she’s not doing something she’ll probably get upset, but this has really left a bad taste in my mouth about both B and Y
Sorry for the long and confusing read, any advice would be appreciated.

If they’re talking about the two of you behind your back or trying to take things you’re interested in (EPQ) and making it about themselves then I wouldn’t take it as a good sign - it might be nothing, but since it’s been ongoing for a while I’d recommend just being cautious.

Is there anyone else in the group (or from other groups) you can talk to? Would you ever consider speaking to B and Y directly?