This is what happens when an already narcissistic person gets a boost of confidence and decides their partner is no longer good enough for them. Granted, LGBT+ support groups are guilty of enabling such behavior, with their perpetual victim stance, seemingly unconditional acceptance as long as you're one of them, and unreasonable demands. But sane people don't gravitate towards such environments and certainly wouldn't trade a healthy relationship for a hollow imitation of a community. I bet 'Beth' was always an asshole, just couldn't really spread her narcissistic wings without a pretext to lord over her partner and dictate her behavior.