You avoid being a dick by avoiding being a dick. It's not rocket science, it's just a matter of how you choose to act.
Failing that, you could at least be an equal opportunity dick, and treat her like any other butt ugly girl you wouldn't want to touch.
For a lot of people, being 'a trap' has very little to do with sexuality or attractiveness; their gender is just a matter of who they feel they are. When they're stuck choosing between 'an ugly trap' and 'an hero', they really don't need any more troubles than they already have.
Besides, she might just be going through an early-transition ugly phase.
I know one transwoman who went from fat and hairy to an absolutely scorching hottie in a few years of hormones, hair removal, and dieting, so a major turn around in looks is possible, at least some cases.