How do you deal with in-your-face evangelical christians ?

The Shield of Religous Belief is a powerful thing and it takes something quite remarkable to it. There is no point trying to have a conversation with somebody like this. It is akin to having a discussion to somebody who is very drunk or psychotic. The best thing you can do is explain to the woman that you are tolerant of other religons but you refuse to have somebody preach at you and if she does it again she is no longer welcome in your home. SHe is the one with the problem not you.