I'm having a similar issue. I took her to the beacon and she heard the voice... we decided to leave and she just stood there. I went to Fort Dawnguard hoping she was just travelling slowly but found her back at the beacon. She spoke about Isran but again... just stands there at the beacon. I've got the summon spell but am hesitant to use it this early in my save (it warns to only use it in emergency situations). What is the danger in using the summon option? Will it break anything?