Practice doodling without lifting your pencil. You will be surprised at how many things can be drawn this way. It is OK to go over lines you have previously drawn. I have drawn flowers, animals, suspension bridges, etc, and I don't think I can draw!
If you can get it on paper, you can translate that to your free motion work.
I always suggest starting with simple shapes, like curves and loops. Straight lines are harder to do using free motion, and are best done with a SID foot.
If you have an old machine which does not drop the feed dogs, simply set your stitch length to zero. This is what I do on my vintage Featherweight.
Not all darning feet will be welcomed by your machine. If she doesn't like one, try another.
Be sure to loosen the pressure on your presser foot.
Good luck, and show us pictures.