Board Thread:General Discussion/@comment-99.25.27.71-20130112015101/@comment-31.49.56.172-20191231041749

You could try Fus Ro Dah-ing her out of the location she is stuck in. Its worked for me in the past.

If not, make a save, part ways and then fast travel a couple of times or wait like 48 hours. After some time has passed fast travel to Fort Dawnguard and she should be there walking around doing vampire things.