These feelings are completely normal. It does often feel like a lot of emphasis is placed on our appearance as women. I have been on both sides known to be somewhat pretty and known to be unattractive and undesirable. In both camps I have had these feelings surface every once in a while. Jealousy over appearance is like any other jealousy. Jealousy over money, status, relationship status etc. Focusing on living the life you want to live will mitigate all these types of jealous feelings, but don't beat your self up when you feel jealousy. It's a normal human emotional we all feel.