@Korut I mean, as someone already said, it was for the sake of her daughter.
I mean, I don't know, maybe killing him sneakily could've worked, but if she was caught in the fact her and her daughter would die, if they tried to escape they'd have a life of fleeing at best or death at worst.
I feel like you expect way too much out of someone, just oh yeah, oppose an emperor with your 1 month old new child. If she didn't care about the child she'd probably manage just fine and would have, but she did decide to care about the child, and that's not unrealistic. Some rape victims absolutely want to get rid of the kids, but some women do indeed become attached to the kid even if they obviously loath the hell out of the rapist, she was the latter, and thus she worked with her lot.
Maybe there was some way for her to manage better, but I definitely don't think it's as easy to get out of that as you act like. The suggestion that she just 'decide to not care about the kid' is a bit ridiculous. That's not how that works.