I mean she only knew him as the villain, in Ains case she thought that he hasn't been turn evil yet. It makes sense that she was wary of him and not wanting to be around him. Did you forget about their first meeting with the bloody body??
did you forget that he made his son the villain right? or that he was first introduced to her with a body bag? maybe you might find a murderer who could kill you at any moment attractive the moment you meet but normal, sane people won’t.
Finally! Gosh she was so annoying rejecting him everytime he just wanted sum love!