Do you think there is still a traitor?

The invisible girl is trash even as a villian.
Seeing kaminari evil and run through his class would be awesome.
Yes, ofc...but MHA is mid, plus having MH academt student as spy and villain at least intetesting plot twist. Also if AFO shared his power with her and made her invisible that is good potential...I mean that girl is like Toby, but right Toby, not that shit Obito...she is foolish right, but also she spend all her life in Academy, and if she still on villain side...well, that is surely much stronger reason than Shigaraki's...
Gonna say this.

The "traitor" is All Might.
AFO probably has a connection to him that All Might is not aware of, like he didnt know anything when Deku said he saw the other OFA users.

Some Voldemort horcrux connection vibe.

Don't know if this was already considered or not, but if not, you've heard it here first.
I guess it's to late for that plot to resolve . Unless if villains again raid in to UA .
This plot can be linked with Eri in the future if author decide to go that way
I was thinking it was probably more related to AFO, or maybe they managed to somehow track the student's locations? Like, placing a tracker on one of them without knowing during the USJ arc when they first encountered the class.