I think you may have misinterpreted that message from them, because that sort of situation does not normally occur. Furthermore, they would not force you into a situation that you don't want to do.
Although it is unlikely that they agreed to be your succubus, you can resolve this by just telling them that you are no longer interested in that sort of relationship. There is no reason to totally destroy your relationship with your GD when you can solve this in a mature and honest manner.
This same thing applies to any sort of problems you may have like this, not just ones pertaining to romantic relationships.
Your GD won't be a succubus nor will any high ranking god though the affection they show may make you think so, plus you have to do a ritual specifically for that kind of relationship
Don't worry if you are not a spiritual satanist you don't have an guardian demon. So no worries no succubus for you, maybe ask them greys to cross-dress for you if that's what you are into?
If you are an actual Zevism get your head out of the gutter, if you actually did receive a succubus you would have to be the one to severely fuck up before she ''regrets'' being with you.