Why would she not pick up on the fact that he's clearly mentally and physically unwell and that trying to make a sexual advance on him in THIS mental state probably is a bad idea?
Like, I guess you could argue she's possessive of him and so wants to make it so she has leverage over him so he'll stay with her, but it just feels like she's taking advantage of him when he's vulnerable, and yet the author clearly wants us to sympathize and root for her over the other options, which, while granted are worse, does not justify her behavior