Give me some examples where he acted like a jerk, since my initial writing sometimes gets changed by the proofreader it might just got replaced, not saying that it is like that but we never know.
But the overall message should be still pretty clear, MC likes her (which you can see when you decline her), even though she's a tease. In the end it should be clear, that she only wants to play around (for now). And since the MC should be aware of that (Anya had no prior interest in him before he moved in with them, Lucy was the one who initiated it), it might be best for you to decline her then, to show her that you're not willing to be her plaything but rather wanted something more (that's why I include those choices in the game). It's not a kinetic novel after all.