Can you geniunely say a Lena that would fall in love with Ian could fuck Robert, Mike, or Louise? She would need to be a completely different person from one scene to another.
Robert is a complete idiot (I know the Robert fan boys are coming after me…) and Lena is completely out of his league, so can’t image why Lana should have sex with him, even if she would be horny af.
I’m not a fan of Robert, and I think he’s had too many scenes with Lena. But I don’t have any issues with the fact that she ends up sleeping with him — I find that quite believable.
It’s several months since things ended with Axel, and she’s not been with anyone since. Now she’s finally starting to move on, and as Ivy not so subtly points out to her, that often involves having sex again.
At the moment Robert tries his luck, it’s a decent option for her. Yes, she’s out of his league, and she could probably have rejected him and found someone better. But the logic of her choice seems obvious: She can skip the job of finding someone else — which can be awkward if you haven’t done it in ages — and it doesn’t feel like a big deal because she’s in no way romantically interested in him. It’s an unexpected, but easy opportunity to get back into it with minimal hazzle. Also he’s decent looking, so there’s no reason to think the sex would be particularly bad.
She can decide that the pluses outweighs the minuses, or the opposite. Both choices seem reasonable to me.
With Ian it’s different: They immediately hit it off because of their mutual interest in literature and music. Even if they don’t become romantically involved later, Lena finds him interesting in a way Robert isn’t. So it’s a bigger step for her to have sex with him. They play different roles in her life.