Ok I'm Christian just so you know. In your second paragraph you said they are free to believe. Yet now when they do, your thinking about squashing it. Let it run its course. Most Christians are good people believe it or not. Heck she may even convert you. Yes, she will probably worry you aren't going to heaven but that shouldn't bother you as you don't believe in heaven.
I'm divorced and Atheist. My ex-wife found religion after we split and is a very devout Baptist now.
My daughter (11.5) is very upset that we're not going to be in heaven together when we eventually die. When I said "If I live my life well and I am a good person, it shouldn't matter. If I'm wrong and there is a heaven, why wouldn't I get in there anyway?" and she came back the following day and said "My Mom said that you can't get into heaven until you accept Jesus Christ as your personal Lord and Savior."
That whole conversation bothers me on many different levels, even if I don't believe in heaven.