I don't think that the Latin heritage has as much to do with your SO's reaction or potential reaction to your new sexual orientation. If you are married, remember just before you got married, when you were making promises? Remember the vows you took? She remembers them. Or if you are not married, remember the vows and guarantees you made even if via patterns of behavior, discussions, and commitments of love? THOSE are more likely why she would react negatively. And those are applicable for most women confronted by a future they did not see when they were getting to know the guy.
Put yourself in her place and look at things from her point of view.
