Yeah, it's called a game for a reason, specially when she has all the cards and knows Jeremy isn't to loyal to his so called bitch of a 'girlfriend'. Why would she play nice to Louise who been a total bitch to her and put on airs and be play it cool? Tell me? Considering Jeremy is the one who sent her the unsolicited dick pic to begin with, and didn't bother to mention he was in a relationship at the time, only to find out about it, of course she is going to put them both through shit. To show Louise that her boyfriend is total fucking trash. And AGAIN, in regards to Ian for that matter, it's entirely up to the player if they want to engage on the possible cheating or not. And even then, if you told Jeremy that Lena was the girl, shockingly he hold true to his bro and refuses Lena there.
But sure sure, she's the manipulative queen and is clearly the evil one... How laughable.