Ok, so I was in Broken Oar Grotto doing a radiant quest, and she got stuck inside after I left. So I dismissed her and she told me I could find her at the "usual place". I waited 24 hours and then checked fort Dawnguard and the Study, yet she isn't at either? Where does she wait at? There really wasn't a "usual place" considering I've had her with me constantly since the beginning.

Ok, well I guess I'll just play without her until I get a quest marker that tells me to speak with her.

Doesn't she wander around the vamp castle?
I read in another thread that you sometimes really have to search... some people have been saying she vanishes but I was told that's not true, you just really have to scour the vamp castle for her.

u can have her as a follower even thou u joined dg