Why is my girlfriend so edgy when I’m dominate [M]

She has a submissive kink, I could tell from the first time we fucked.
From the jump, she told me before we started dating she was in a throuple before with another guy and girl, who were really into bdsm and humiliation. She was like their “toy” but they dumped her when they found someone better apparently. When she talked to me about it she acted like it’s something she regrets. But I know those bdsm and humiliation kinks still turn her on.
That doesn’t bother me. What bothers me is constantly whenever I try to push boundaries and expand our sex she gets visibly uncomfortable. She even broke down crying like a week ago and said “that’s what he used to do”.
And all I did was cum on her face… literally for the first time since we’ve been together for 4 years…. like what? You’re still thinking about that?
I’ve always been cautious with the things I do because of what she describes as a bad past. The other half of me wonders and wants, should I just go full alpha on her like I want to, despite what her past experiences are?