itishe, I have dated virgins before.(Well past the age when they should have been) . . don't worry about it.
Keep escalating, don't ask her. She will tell you eventually(most often in a conversation where she explains to you that she moves slower than other girls). At this point she probably assumes you know she is, I'm assuming she is of course, the behavior sounds familiar.
There are 2 types of virgins that you will run into. Those that feel strongly about there virginity and those that don't. Those that don't will generally take some time, but they will sleep with a guy who they feel strongly for.
These girls are generally virgins because they have never really met or been involved with someone they felt that way about.
Girls that feel strongly about there virginity are a harder case to crack. I hate to say this but it sounds like you might have one of these cases on your hands. The reason I say this is that the first type will go with "what feels good" as long as it stops short of sex. The second type will stop you quickly when it feels good. She might feel like you are the one but her main barrier is that "she is just not ready"
In either case one thing I am sure of though, virgin women make GREAT girlfriends(much better when they aren't virgins anymore). It will take some patience on your part but when they open up . . . WOW
One more thing . . . Ultimatums about sex. They will only work if you walk away and are willing to. . . after some time apart she may decide that she wants to be with you more than whatever it is preventing her from having sex but chances are at the moment you give the ultimatum it won't happen.
