Tom,

I agree with others here that she’s possibly not telling you the entire story or is very careless. With STDs being on the rise, who the heck does not use protection with a one night stand?? I’m shocked if that is the case.  I’d offer her your friendship but not more until you get to know her character much better. I’m not a parent but have witnessed how a child changes the dynamic of a couple. The child will always be a # 1 priority to the parent (s) and this child is another man’s.   Good luck to you.