I adore Trinket as a little girl. I'm not sure why Trinket likes Mender, except that she likes him only because Ember likes him too. I'd say he doesn't have much meat on his bones, but he doesn't have much bone on his bones, either.
Nevertheless, if a Troll from my family wanted to spend the rest of her life with an Elf, I'd have no personal objections. I just don't know what type of accomodations we could offer. It was probably easier for the Wolfriders to live among the Sun Folk than it would be for an Elf to live underground. Nor do Trolls slip deftly between the branches of a tree.