Maybe Bern is going through a random sexual identity crisis? Or wants to make May happy so they'll have hot orgies with cute university girls?
Nah I don't want to see such cheap thing in Flipside comic, like Crest won't suddenly turn gay I think, so why Bern should turn out bisexual all of sudden, she is not a teenage kid, she's a full blown woman who knows what she likes.
As for second question if by any magic it would happen, it's obvious it would be Glyph, or maybe Crest would turn into predator beast, who knows
If any I would want to see that leader in which Bern fallen in love to appear to see how Bern would react
I rather think Bern is in overall depressed about what happened, she wasn't strong enough (again) to resist a spell and she cheated on May in her way of thinking, and it seems they didn't have any time alone to clear these things out, I think for Bern it's big case and she's just thinking about it too much, like she compared earlier her lie about loving that leader bandit with May constant cheating habit.
Plus she may see her father again, which too isn't easy for her, not mentioning whole town full of magic.
So yeah she seems to be in a pinch.