Depends on the girl and the person asking, I would just be honest, If they are a huge huge part of your life and losing them would be a large effect then tell her, If they are very minor and she is worth far more then they are, Tell her that as well.
As missy said stress honestly how much of an impact they will or wont have, but above all be honest, And also between me and you if you get a girl who is willing to dump you over one thing like this do you really want to spend life with her? What happens if you get sick or injured? What happens whem you get old and your looks fade? What happens if you have a hobbie she hates?