hi we are going to the st lucia this summer and my girlfriend wants to go topless on the beaches, is that allowed / accepted? heard a few different stories!

No...I believe not. Most islands that were part of the British empire do not allow topless/nude sunbathing (Cayman Islands, BVI, St. Lucia, Bahamas etc). Islands that were under French or Spanish rule generally do allow topless sunbathing (Mexico, Domincan Republic, St. Barts etc).