Forgive me, I did read that she broke up with you (so sorry that happened) and read like most of the first page of replies (so not sure if someone mentioned this) but I feel like BDSM for her may have been her way of reinacting her past. Maybe blood was a reminder of said past. If she does come back, I'd mention the possibility of BDSM being a reinactiment of her past and maybe the reinacting went too far and it triggered her into an area she isn't familiar with or didn't process in therapy yet? If she comes back, maybe talk about not doing BDSM?
I am so not saying that BDSM is trauma reinactment for all CSA survivors and that CSA survivors can't have healthy BDSM sex. But, just maybe this wasn't healthy for her. Just maybe. Just a feeling given my own reinactments of my trauma and how I reacted when those reinactments went too far.
Reinactments of trauma can make you feel safe because they are your normal. Except for when they don't make you feel safe and in an instant make you feel very unsafe and you bolt for saftey!