Hi Papillon,
Welcome to the forum.
There are many, many members of this forum who have been in abusive relationships and yet find satisfaction with a non-vanilla partner.
BDSM means many things to many people.
What type of sadist is she?
Mental?
Physical?
Both?
What about you? Does her sadism turn you on?
Are you a bit of a pain slut when you play?
A lot of a pain slut?
Do you like mind games?
I suggest that you take your time, go slow, do your research with your partner asking her lots of questions and researching on the web.
Take a look at some of the "check lists" out there and see if anything turns you both on.
A word of caution, abusive relationships leave triggers and we don't always know what they are or when those mental buttons will be pushed. Make sure you and your partner know your mutual concerns.
My own pet, Nathaniel, was in a not-always consensual and often extremely abusive relationship. What turns him on in fantasy play, isn't always what he wants in real life and has been known to trigger some deep issues.
The keys to moving forward are forgiving yourself, forgiving your partner, and learning from the situation. A good dose of laughter and sometimes crying also helps.
Have fun,
Ruby