I think you should protect yourself. You are not being unkind to this woman by not going out of your way to help her. You are being kind to yourself and protecting yourself from someone who is harmful to you. The Dalai Lama (or someone) said something like "be kind to everyone. if you can't, then at least don't harm them." What you're doing is just not engaging with her. You aren't harming her by doing that. Just because you're not outwardly kind to her doesn't make you an unkind person!