Got some potential but here are a few suggestions.
1. I think you are over processing your images. The skin tones look way too red and the skin smoothing is a little too much. Unless the model has the most amazing skin ever, in which case they are fine.
2. Image one best of the bunch. It almost looks like a lifestyle image, facial expression so-so, but its nice.
3. Image two, lighting really doesn't match the mood. Also, minor detail, but if you moved her a few inches left or right the seat post wouldn't look like it was going you know where.
4. Image three also has potential, but the follow elements distract from the image. Exit sign is very distracting, it shouldn't be there. Lamp coming out of her head is distracting. Hot spots in lighting distract from overall quality. This would have looked great with simple clean sunlight or shadow under an awning or umbrella.
5 Image four is an awkward pose. Cute girl, but so-so on her body.
6. Image five is OK but the color is off and the background distracts the viewer.
Good start, just a few little thing make it better.