LGBTQ people who support Trump must have a reason. IMO that reason probably boils down to a lack of empathy and/or lack of critical thinking skills.
So now the question for you is: do you want to be in a long term relationship with somebody lacking one or both of those things?
You're unlikely to change her, the only person you can control is yourself.
This isn't the same as The Boy Cried Wolf.
Unless you're talking about a version of the story where there really were wolves every time he cried wolf and nobody believed him until the wolves were eating people.
Still not a perfect analogy but much closer.