She loves suffering.
Even better: she loves suffering for me.
I have written about sadism before (see “On Sadism”), where I talked about the importance of reactions. That’s the point: she gives me genuine reactions to the suffering that get me aroused. She gets off on pain, violence, degradation, and helplessness. She doesn’t smile, giggle, or laugh at these things; she moans, cries out, winces, and tells me how much it hurts. Her body language tells me that the things I am doing to her hurt. They are all the kinds of reactions I look for in sadomasochistic play. Oh, and don’t forget the pain-like reactions that come from intense and multiple orgasms after edging.
I can’t tell you how many times people have told me that masochists are terrible partners for sadists, because sadists aren’t supposed to inflict pain on people who like it. I can tell you exactly how wrong they are. If you’re inflicting pain without enthusiastic consent, you’re engaging in rape with a victim you’re coercing. If you have enthusiastic consent from someone who wants to suffer for you and gives you all of those reactions you look for in a partner, you’ve having a health BDSM relationship.