I mean, Maya Prime has admitted to killing Senseis before just because she was horny:
She had a kill count and she had possibly millions of years to add to it in whatever way she wanted.
I wouldn't be too surprised if Maya Prime just realized that getting rid of everyone is pointless when they'll come back, and she still won't have Sensei to herself.
Personally, I think if anyone is a slasher, it's probably Maya (or Kaori).
As for New Maya, besides not really knowing Sensei is seeing others, she also probably doesn't know that if she gets rid of someone, they'll reset, since she doesn't seem to buy the resets quite yet. There's a lot of untapped potential with New Maya.