I think they are REALLY good!! And your mom is right, artists always are hardest on themselves. My sister never likes any of her work and she is (or was, she doesn't draw too much anymore) very good. She entered one of her charcoal sketches in an art show and came in second. After seeing what came in first, my sister should have been first. LOL

But keep it up. With as good as you are now, you will only get better and better with more practice.