Now, submission is a very particular beast... mayhaps you aren't particularly sure what the terms 'submissive' and 'submission' actually mean. For example, there are bottoms who will be passive... you can drag her to your knee and hold her down for a spanking but a submissive will climb on your lap of her own volition and present herself to you.

There are people who are into kink, they like being tied up or spanked and the like but they don't offer submission... do you see where I'm coming from?

The final verdict is that you can't turn someone into a submissive, you can't make them into something they are not, submission is offered, it cannot be taken because that is contradictory.

Talk to your girlfriend, ask if she might be into a little spanking, a scarf to the headboard, having her wrists held down, or a hand clapped over her mouth, or being blindfolded and see where it goes from there.

Does she become aroused when you tell her to do things in the bedroom? Can you say "I want you to go lock the door and strip naked for me then come here and take me in your mouth" or would she just tell you not to order her around?