Lena is not your character. These "maybes" have nothing to do with who Lena is as a person, at the very start of the game. I somehow doubt that you could rewrite your personality into something you're not. Your personality is consistent. Same thing with ORS characters. Lena finds connection with Ian, Holly, Emma, and Ivy. This is her people, because Eva decided so. And that means that whatever happens between them will depend not on Lena's random whims but on series of events that shape their relationship. Lena can mess with others because they're simply not as important to her. She has reasons to hate Stan by trusting Louise, she has reasons to dismiss and treat Louise badly because she's stupid and clingy, she can make Mike cheat on his girlfriend because for her that girlfriend is a nobody. There are objective reasons for Lena to act within her character. She can steal money from Ed and Molly because she can be desperate about money thinking it's no harm if they're about to close anyway. This kind of internal logic guides EVERY decision in this game. NOTHING suggests that Lena likes to be a cheating slut, in fact she DISLIKES cheaters based on her past experience. For something to apply to Ian / Lena, there has to be an established pattern of similar behavior or some form of predisposition towards it.
If she didn't care about others' feelings, she wouldn't hate Ian for sleeping with Holly, which happens by default if Ian ends up kissing her. Holly and Ivy are two people in Lena's life that she trusts and protects. Just because you want to play Lena like a psychopath doesn't mean that she IS a psychopath.