Knowing how Jill loves to be the goody two-shoes, she's probably thinking over whether she'll report Bella or not. Or she could make Bella break up with MC, because the relationship is unethical.
Nah, I don't see Jill ratting out her best friend and possibly ruin her life just to comply with rules, even she wouldn't be that fucking naive.
She's probably just feeling very confused and conflicted (and in case MC pursued both of them, very pissed for sure) because of whatever past Bella is hiding.
Plus bella affection to the mc never made any sense at all from the beginning. He was caught doing stuff in which Bella's eyes is the type of person she hates.yet we're here at the end of episode 8 with bella.
Although humans like to boast about their rationality, at the end of the day we're all still animals with very primal needs and instincts.
Bella completely shut off her lust and emotions for other men for 3 years(?), as soon as she was kissed by a drunk MC a lot of those repressed emotions came back in force and she started to fall hard for him, and as soon as she realized he wasn't really a bad guy she just started resisting less and less.
It's not that hard to imagine this situation happening in real life really, I've actually seen something a bit similar happen.