Shadowheart, probably. She and Lae'zel are the only ones with both decent introductions and legitimate reasons to join the group, and also the only ones who interactions with my PC don't feel fucking janky for one reason or another.

If Lae'zel was given more dialogues (and i more options to call her out on her obvious greenness, god forbid), she'd probably edge out. I like her personality the most, bar the cringy jealous talk and BDSM stuff.