Teach respect: Another part of helping your daughter develop healthy self-esteem is teaching her to respect herself and her body. Discuss how others should treat her, both physically and emotionally, and that how she portrays herself on social media can impact this.
Respect her privacy: Although you might want to push certain conversations at this age, you should also start to respect her boundaries and the choices she makes with her body. Let her know that you are always free to talk, judgment free, but don't make her feel like talking is required or will be used against her.
Play the devil's advocate: Whenever she expresses displeasure with a physical attribute, acknowledge her feelings but also remind her how lucky she is to be happy and healthy. Pointing out something that she should be grateful for and bringing up how people always want what they don't have — like those with straight hair always wanting curly hair or those who are tall wanting to be shorter — will help put her "problems" into perspective.