Tbf she barely shows up in the game, I don't blame someone for not recognizing her. Shit, it could've been worse, like using Pink Sweater Guy as the culprit.
We meet Beth in quite a few important scenes, in fact.
We meet her at the cafeteria in a couple of scenes: first meeting ever with Sage; a scene with MC and Bella.
We meet her at the DIKs' party when the Cathy's cluck incident happens.
We meet her at the dorm party.
We meet her at the gender study class exam.
We meet her at the end of episode 10.
Honestly, she might be the most important student character who is NOT a love interest / a DIK.
Now that it's been pointed out, it's pretty clear that it's Beth. For some reason, I missed her when looking for redheads in the Bios.
Mona doesn't look like the girl we see with the posters - I was torn between Elena, Ashley, and it being some minor character that hasn't yet been significant.
The real question is who's feeding Beth stuff from inside the DIK house - officially, only Rusty, Tommy and Tremolo still have free access to the DIK laptop, though if someone snuck some spyware onto it that wouldn't matter.
You guys might want to replay the whole game from episode 1 and pay attention at the characters appearing in the background and what they're doing.
Pay attention at the parties. Who is who at the Halloween Party. Note: if I remember well, we don't meet Beth at the HOTs' party.