I don’t think she was just randomly gay, and just because she had a boyfriend before, doesn’t mean she can’t then date girls. Many people start dating to follow societal norms, though since marriage came up, she probably genuinely liked the guy enough to broach the subject. Also, during their interactions at the resort, she never shied away from being intimate with her. In fact after the first kiss, she seemed like she really wanted to know if it was something more, or just a Spanish custom. She even invited her back to her room to confirm. So I think she’s probably bisexual. We don’t really know much about her backstory, other than she had a boyfriend prior after graduating and working. No idea what her relationships were like before that.