Hey guys, I think i need your opinion.

Past saturday i take the subway back home and there is this beautiful girl sitting with a not really good looking guy that i tought was her BF. Me and her kept exchanging looks and smiles. Me and her got off at the same station and took the same bus. On the bus we kept looking at each other. I didnt went to see her cause i tought that guy was her BF. So when i came home i opened my tinder and then BAM she liked me. Of course we talked on now i got a date with her on friday nite (yay!). So when is it ok to ask her if shes seeing someone else ?