Is this cheating??

So my brothers new gf is very... ig wild. She’s honestly just straight out a hoe and I’ve seen her in snap vids get really handsy w ppl.

Well I’m one video she’s making out with a girl. Idk much about his gf but I’m pretty sure she’s straight. Ik my brothers never really been comfortable w confrontation, especially where as this relationship is new and he seems to really like her.

But this just got me thinking, is this still cheating? I’m pretty sure it is, what to u guys think?