I guess I'm just ugly, then.
As others said, the companions can just not be interested in you or reject you, if certain things are happening. They also can end a relationship, if you behave in certain ways - those mechanics are actually pretty good.
The only thing, that is a bit jarring is, that you have to lock into a romance during the tiefling party latest ( apart from the late comers Halsin and Minthara). In my first run, I found Karlach shortly after I freed Halsin and had the party and during doing side quests. I know, where she was, since I played early access and a friend told me, that she is still in the same spot, but somehow, I ended up doing the main quest before doing the Risen Road.
( And your gith lady is gorgeous)
