Many years ago I read a book about grad students who time travel - sort of - by inhabiting the minds of people in the past. If I remember correctly, there are scenes involving either Queen Victoria or Queen Elizabeth the 1st, and Joan of Arc. Also, one of the grad students is dating a guy who turns out to be the mind of a man from the past stuck in a present-day body.
I read the book sometime around 1995, and I don't think it was a new book at the time. I would say it was from the 1970s or 1980s.
The main characters were two female friends or roommates at their college. One of them is in danger because the mind she jumps into is fighting her for control of the body, and she may be killed while she inhabits the body in the past.
That's all I remember, any help would be appreciated!