(13M Arom) Why are some people like this

BASICALLY, I'm one of those insanely quiet people who have their friend group where they're a normal person nd all onliney and stuff. So I have this friend (13F, very funny, my complete opposite and I enjoy her company), lots of my friend group in girls, (It's the "Music group" what we're called by others) so since Wednesday till today, there are music exams, so we can't go in the music room, yesterday the library was closed so me and her just sat outside in the playground on the bench and we just started talking about CRK, music, and just stuff. Time to introduce some *Characters*

Me (Me/I/)
Friend (Friend)

Z (Z, she's in my form and I was chill with her until this)
Z's friend (Idk her name so I call her this)

T (Some golddigger pick me who likes me idk y but she's annoying)
S (T's friend who is also annoying, T and S hink they're funny and cool)

So me and my friend were talking about what i said so Z and Z's friend are like covering their mouths and looking at us CLEARLY they're talking so they walk past us laughing then Z's friend comes up to and she says

"*Laughing* I... I-s that your g-girlfriend???" *Walks away to Z laughing*

So my friend just shouts to them as they're walking away

"Are we not allowed to have opposite gender friends!!!???"

So we talked about that for like 4-5 minutes and then T and S come up and they're like,

"OMG, [My name], is that your girlfriend? Are you guys like uh DaTiNgGg or something"

So my friend get annoyed again, she said the same thing, then we rant on about T and S for a while. Then these pick-mes come back and then they're saying bull and go away. Then this group of those loud footballer boys came and start saying stuff INFRONT of us ABOUT us.
Like, can y'all not think about relationships, I think they just picture stuff that they wish they had. I absolutely hate these kind of people. So I didn't go school today.