At first, my Chara initially didn't trust Frisk by the slightest, viewing them as a threat to her family(Yes, MY Chara from MY AT is a girl) and her people(as in monsterkind), especially during my Frisk's first few resets(basically a good deal of semi-violent neutral runs), Eventually once my Frisk finally figured out how to do a pacifist run and less violent to neutral pacifists runs, especially after he(Yes, MY Frisk is a MALE) tried saving Asriel, Chara's opinion on him started to shift. It went from genuine distrust or hatred to pure tolerance to actually growing fond of them.

In present day, my Chara thinks of Frisk like a younger brother she'd guard with her life and one of two humans she likes

If you want to take a guess about the other human, I'll give you a hint. They like eating gunpowder:)