It's very usual that nobody asks "Gotra" before they fall in love with other. Have you heard of anyone ending up their relationship just because of "Gotra" ?  They are absolute turd. If you are so much concerned  about this whatsoever called "Gotra", It won't be a problem for you. I have seen it before. You will be asked to perform some rituals "Puja" and you will be allowed to marry her. Consult with you priest. G.L