I am sorry you are worrying you may have made a mistake. I think there are no "mistakes" in relationships, everything that happens can be a learning situation.

I don't know your girlfriend and "why" she has made/is making ultimatums in this way. Did you ever ask her or discuss it with her? I don't know how you can say you would have been proactive in going forward toward getting married if she hadn't made her ultimatums; we cannot know what we would do/would have done in other situations, we can only imagine what we would have liked to have happened? But you have stated you wanted to go slowly so I can't see why you would have been going any quicker than you have gone.

Yes, her pushing for marriage when you did not feel comfortable was definitely a turnoff! But I still do not understand why you did not discuss all this; why you did not tell her, "Your ultimatums make me uncomfortable and, if you would like for us to marry, are making it harder for me as I feel you are more interested in getting married than in being with me" or something like that?

I'm sorry, too, but I almost have to smile that you worry about possible future ultimatums from her if you "give in" to this one? Other people are going to do "their" thing but if she gives an ultimatum about something else, why would you have to "give in" to that anymore than you have to this? You have your own will and agenda (or you would be getting married in August :-) and while it sounds like you are perhaps a bit more "mature", she is going for what she wants?

I still think a frank, serious discussion of ways/means/ends could come up with a plan that would work for both of you? If you have a discussion and get her to agree to "outlaw" ultimatums (in agreement that you "move" within a certain period of time; sorry that that, in itself is an ultimatum of sorts but you can't have forever, no matter how scared/scarred you are from a previous relationship! S or get off the pot?) and get her to understand how you feel and you understand how she feels and what exactly is going on could save the relationship for both of you, if you want.