You're a very good mom and your daughter is lucky to have you supporting her. So many of our parents/families/friends are unwilling to understand us. My mother in particular doesn't really acknowledge my illness(es) and likes to make me feel like I'm burdening everyone (I'm 21 as well). My best advice would be to continue supporting her and to never make her feel as though she is a burden. Be firm but kind. Let her know her feelings are valid, but that other people have feelings too. She wants to feel loved; she just experiences emotion more intensely than other people, and that is very overwhelming.