Do I tell her I'd love to date her?

Tell her anyway! She specifically said that the her and the other guy were not exclusive. That is an open door for you. You definitely do not want to keep it inside anymore, especially if you feel so comfortable with her and share everything. It's definitely worth the risk! If she doesn't reciprocate the feelings, your friendship will eventually go back to normal, even if it is difficult at first. And if you never tell her, you'll always wonder, "What if?" and you'll be driving yourself crazy forever. Go for it! :)