On the contrary, engage her more. People challenge you because they want to be able to defend any change in their own beliefs should it come up.
Use the question method to draw her out. Keep asking why. Paraphrase what she says. Also, repeat her last few words of every sentence to get her to keep talking. You need all these skills anyways. Pretty soon, she will avoid you because she may learn you are the strident one who wants to change hearts and minds.
Take a course in apologetics. Important topics don’t stop for anything. Think, “this may be the last time I have to change her mind.”
If there’s something you don’t know, say that you will find out. Also, do a lot of listening. Most people talk themselves into a corner unaided.