Well I don't know that I have ever encouraged anyone to steal a cat but I certainly do in this case!!! If the cat keeps running to you and this lady waits days to even come look for her then she might believe that she could have been hit by a car or just run off since you haven't been home.
I'm not going to get into a very long and heartwrenching story but there was a kitty that kept coming to me and I turned him away too because I didn't want to cause any waves. The story had a very unhappy ending and he died. I still to this day see his face and hate myself for what I did. I like to think that he is why I try so hard to help as many as I can so he didn't come to me in vain. It has been years and I still can't forget him. I don't wish this on you or anybody! She is coming to you for a reason.
She surely will end up pregnant very soon and how will this woman treat kittens? You can stop a tragedy before it happens. We don't often get that chance.
The decision is yours and you know we will support you in whatever you do. Good Luck!!!