I fantasise about dominating my fiancée, but she told me she was sexually abused when she was younger?

So the post says it all really. Our sex life has always been good, although I do suffer from delayed ejaculation. Through solo exploration I have discovered the kind of thing I enjoy is man-dominant stuff, to do with the fact that I'm not normally the take-charge kind of guy so the idea of being like that really appeals to me.

Here's the problem though - early on in our friendship before we got together, she told me she was sexually abused when she was younger and refuses to get counselling for it as she doesn't want anyone to know, including her family. Not really a problem in itself as I only have to avoid a few trigger factors so far which is not difficult. But she's now asking what my fantasy is and she really wants to try it since it may help my delayed ejaculation. However I find myself scared to try anything in case I bring up demons of what happened to her. She has said that she will just tell me and we can stop anything that scares her. However I know if it comes to that, I will be so upset that I reminded her of that, I REALLY never want to hurt or scare her. How can I just get out of my own head and not be so scared? If she hadn't told me what had happened to her I don't think I'd be having this issue although I really appreciate that she trusted me with the information. How do I get past this?