If the only reason that you don't want to go out with her, is because of the way she looks, that's pretty sad. You'll probably miss out on a lot of great things in life if you go around judging just by the way they look.
In any case, all you have to say is that while you are very flattered that she's interested in you, you just aren't ready for a relationship right now.
well i would say " yes" unless i have a girl of my own but if u dont then just say yes and see about her actions and personality and see about if u want to go out with her or not it's always about what's on the inside not the outside only. remember that. homeboy