Interesting question. I would say, discuss this with your girlfriend and see if she is okay with your work of her being sold. She may be flattered and art that has passion behind it is always the best art.
The other idea that I have that may help you move back to landscapes is paint landscapes with your girlfriend as the lady in the picture, but with it being an image that is more about the place and environment she is in. Some examples, maiden running across a field of flowers, maiden resting by a pool of water, hero woman conquering a fear as shown by a location and weather...etc.
Just a couple thoughts I had. Hope that helps.