Firstly I would leave well enough alone. If she was gonna do anything she would've done it already so if it ain't broke don't fix it. Just try to learn from the experience.
As to the scenario well look, as radeng points out, she was DTF two guys in a session so she couldn't be all that innocent. She was into it at the time and that's what matters. It is a natural tendency of girls to rewrite the past to fit their current emotions, and what seemed like a great adventure at the time could well feel slutty to her now. So be it. No need for you to get drawn into her emotional issues. Stay strong.
But I now want to discuss dominance a bit. The best kind of dominance is through least effort. If you simply expect to be obeyed and have the vibe to match, then generally you won't be questioned, she'll just hop to it. This is what girls really like. But if she's quite spirited, or for whatever reason things don't go your way immediately, then the next step of dominance is to be chilled and give her some consequences for not complying. Again least effort is the key here, you might need to wrestle her onto the bed or something, but your goal is always to gain compliance, once she's complying then there's no point being rough about it.
Another way to exercise dominance is through persistence. As I see it, if she's not complying then you have two options: Either persist or do a takeaway. If you choose the route of persistence you can be totally calm and chilled about it, but just obstinate as fuck. Let her understand through your actions there is no way around it, you will be continuing until you get your way or she leaves (obviously, she can always leave at any time -- and if you're tying her up or slapping her something of that nature, which women love, you must make sure she has a safe word). Again, least effort -- don't be excessively rough with her at all.
As to physical roughness well it's fine to spank/slap her, pull her hair and so on, but in my opinion you should not hurt her, and also, leave emotion out of it, never get angry or carried away in the moment. I also wouldn't advocate stuff like digging your nails into her back or biting her nipples or whatever. If you must do this kind of stuff, do it gently -- I have had success with clothes pegs on the girl's nipples but if you're going to do this, try it on yourself first, you'll find it doesn't really hurt -- what would hurt would be things like twisting them etc, which I do not recommend. Verbal game is good, such as telling her she's gonna have a red bottom and then following through (you can do this without really hurting her).
I would regard things like slapping, hair pulling, clothes pegs, ropes, etc as basically props which help to set a scene and establish your dominance (consequences which you use to gain compliance). The other thing to keep in mind when using this kind of tech is that you should have a story behind it -- secretary was late submitting the report and so she receives a spanking, or some such. I also think if you're going to introduce dirty words it's best to have her say them, I wouldn't just call my girl a slut, I'd order her to say "I am a slut and I want to be fucked". Thus you are gaining compliance from her, instead of making her feel abused.
If she says she likes it rough it probably just means she wants a really good pounding, I would recommend reading the article on adapted missionary on the main site as this will give you the tech you need to just pound her hard without getting excessively tired. Destroying a snatch basically means being good and hard and fucking her as deep as you can go, and really grinding that clit against your pubic bone with each stroke, and sticking at it intensely, staying on rhythm and preferably establishing good eye contact as well, until she comes. I would go pretty slowly to begin with, just focusing on getting as deep as possible and grinding her hard, and gradually speed up as/when you both want.
Hope it helps!
Ray