Speaking form personal experience, the breathing meditation you did is what spawned the ability to be mindful of your physical state.

I'm very certain that you don't have personal experience of what spawned her mindfulness of her body.

Breathing meditation is certainly a way to develop it but it's not the only way. Body scanning is probably partly responsible for her gains in that area.

Be careful of image meditation. If you choose to go beyond halfway through the path of meditation, you will have to remove all of the images you accidentally lock into your body.

What do you mean here? I would just avoid visualing negative images. If you visualize something positive and it doesn't disappear there no harm done.