I feel like the exceptions to "hypnosis can't make you do anything you don't want to do", fall under "it's entirely possible to be an abusive relationship with a manipulator/gaslighter".
Like, there's plenty of ways to manipulate you into doing stuff in an abusive relationship, and hypnosis is easily the most difficult method. I don't think hypnosis would even work remotely well if you didn't at least 95% trust the person doing the hypnosis and/or your ability to reject bad suggestions.
An abusive person has much better ways of manipulation than hypnosis, which mostly just yourself doing thing to your brain willingly. You can do a lot of stuff with hypnosis, like setting up your own traps and surprises for times when you've forgotten something, or are in a different state of mind, but it's still you doing it at the end of the day.
So yeah, unless your girlfriend is Putin and she has you in a cage a mile below sea level, you're probably going to be fine. Communication is the key.
That said, hypnosis is super intimate, you're both exploring your brain together. As with any relationship, hypnosis or not, you'll both share a lot of experiences and come to see things from each others points of view. This might be a problem if the love is one sided?
It's entirely possible for someone to convince you of something you wouldn't have believed before, just like it's possible for you to see the other person's point in a debate.
I'm sure the submissive element probably comes into play too, but it's hard to tell how much each element effects what. There's not really that much scientific research on hypnosis, let alone erotic hypnosis, let alone niche bdsm hypnosis.
No one here really knows anything for certain, so keep us posted and don't be afraid to share theories and opinions. It could be that I'm completely wrong, but this is all my best guess based off being in erotic hypnosis communities since I was like 12 and reading experiences and articles and shit.