Well, you answered your own question in part, because you already know that’s not true. I know that knowing something logically and knowing something emotionally are entirely two separate things, but she was abusive, and that was abuse.
What’s going on here could be one or a combination of two things: either she altered your internal sex compass, or she was a partner who fulfilled some latent fantasies for you (especially if she’s been your only partner), so she’s your best fantasy frame of reference.
Tackling the second one first, I’ve had all of two sex partners in my life, and the second (my most recent ex) was my longest sexual relationship, and the most fulfilling for me, even though on a lot of levels neither our sex life nor our relationship was really fulfilling for me in the end. Still, when I think about my sex life and some of the things I do and don’t like, who’s my best and most recent frame of reference? My old ex. Doesn’t mean I never enjoyed our sex life, and as a matter of fact I did get satisfaction out of it, even if it wasn’t perfect. The same thing is likely going on here- you’re reaching for a certain image for a certain scene, and her face floats up because it’s the best frame of reference you have. Just because you enjoyed your play together enough to still find it arousing doesn’t diminish what she did to you.
The first one is a little harder for me to pinpoint as an outsider, and requires the most internal investigation and potential work if it’s true. What I mean by your internal sex compass is what you personally find sexually gratifying, regardless of whether or not that involves fetishes. The activities and fetishes that come naturally to you, those are your own internal True North. Sometimes those are just latent desires that can be innate (for example, who the fuck knows why I love bondage so much? I just do), and sometimes they can be triggered by something you’ve seen or been through.
A common repercussion of abusive relationships- particularly sexually abusive- regardless of whether or not the relationship was a kinky one is that the abuser will alter the abused’s sex compass in some way. Maybe you previously enjoyed giving head, for example, but your abuser was really turned on by making you deep throat them over and over until you vomited. If they do that enough times and exert enough control over you and your life, that can be the only way you get off as well. They subvert your own desires and pervert them to be a shadow of their own, of what they’ve made you do and what you’ve been through.
Only you can tell which of these two options is going on, or whether there’s some bleeding of the lines happening. It doesn’t change the fact that you were abused, and of course it doesn’t change the fact that it’s upsetting while it’s happening. You want to move on and have a left separate from her, which includes your sex life and your fantasies. Unfortunately, you may never be able to get her out of your head completely, but that doesn’t mean it’s going to be impossible to get her out of your sex fantasies. It just involves a lot of work, maybe some therapy, and hopefully some better experiences to help put better images in your head and find your way back home.