I have seen this quite often. The doggie purses and doggie clothing and silly things are not what the issue is, for the dogs. I say good for you that you have dogs that tolerate that sort of thing!
Groundwork!! Collin is correct in that this is a rank issue.
One question - do the dogs obey her better/moreso than they obey you? Or is this just that the dogs follow her around and want attention and affection from her? You say they "mind" her I am assuming you mean they do obey her? If so, how long have you been with your girlfriend where she is around the dogs very often? What sort of time frame are we talking about here with the dogs becoming lax in their OB with you? (I.E. several weeks, months... overnight..)
A dog will "prefer" a human they can walk all over. It may not seem that they are acting in a dominant fashion but if a dog "demands" attention and affection, it is saying "Pet me, NOW, human slave!" (err, well you get the idea
) A line must be drawn between loving a dog and wanting to be affectionate towards it, and submitting to the will of the canine to be loved and scratched and massaged all the time. If this is the case both you and your girlfriend need to do groundwork and establish yourselves as the leaders of your dog pack.
If that is not so, and the dogs are obeying her and not simply following her around wanting affection all the time, and the dogs were yours prior to her coming into your life, more than likely what has happened is you have been replaced as Alpha by your girlfriend.
Not saying your girlfriend dominates or is the boss of you, but 9 times out of 10 a new addition in the way of a girlfriend or boyfriend means the owner changes their demeanor somewhat, and the dog owner will try to make sure those dogs behave and "mind" their boyfriend or girlfriend, they set the person up as being dominant over the dogs. You can wind up drifting away as leader of the pack by having a new person come into the picture that also acts as a leader. That is a very simplified way of putting it. Essentially you are either no longer alpha or are in limbo.
You need to work with the dogs in OB and do groundwork
(http://leerburg.com/groundwork.htm) and re-establish yourself as leader of your pack. This does not mean your girlfriend should no longer be an alpha, though. It isn't a competition of who is the stronger leader.
A dog is more likely to follow a leader that is strong, yes, but also "fair" and what I mean by fair is a leader that does not become angry or aggressive, you should never pick a fight with the dog. Possitive reinforcement is great for setting yourself up as a calm, assertive alpha, one the dog can trust AND respect, and not fear. BUT a dog should also never be allowed to get away with not following OB, ignoring, or confronting the alpha.
It is finding the balance between affection and correction, too much of either causes problems. The way you take care of situations with your dogs, such as not obeying, ignoring you, etc, will determine how your dogs view you.
I think you should talk with your girlfriend and explain the situation, that she needs to allow you to regain your place as a leader for your dogs and need her to allow you time with your dogs to do so. Meaning not lavishing massive amount of affection on the dogs constantly, or not overriding your possition as alpha, and allow you to work with the dogs, either without her around or with her not in close proximity.