>>42454266
There was this gay fanfiction I read where Fluttershy takes care of an injured Trixie she found in the woods after Boast Busters. It gets pretty gay, but they do have some good moments where Trix, never experiencing kindness like that before, doesn't really know how to take it, and warms up to Flutters a bit too much. Can't remember what it was called.
>>42454383
I wouldn't say she needs someone to challenge her ego to be friends with them, she just needs a friend who likes her for her and to show her kindness. Trixie's problem is that she seemed to push other ponies away, and Glimmy was the first one she felt she had something in common with, which allowed her to start opening up to others.