A "curse" is not necessary in this situation. Since you practice magick, I'm pretty sure your glares at her and negative thoughts have sent enough small curses her way unconsciously.
The other thing you mentioned was a revealing spell, something that removes the facade she creates for herself so that others see her for who she is. Mind you, it is still not kind to remove her mask. Those who act as she does are not comfortable with who they are, they usually have low self esteem and act this way to pretend that they do not. They strive for others approval and attention in order to fill what they lack in their own views of themselves. Positive attention from others makes her feel good about herself, and she'll get it anyway she can, no matter who it hurts, because she herself is hurting and she cannot see past this. It is a way to protect themselves. Removing it may cause her to act out or hurt herself.
Feel sorry for this girl, because she is already living an unhappy life. I would suggest that, if you continue to feel a desire to do something, that you perform a spell to help HER to see that her ways are not good, and that she needs to make changes. Ask that help comes into her life. Not only will she be better for it, but so will you, because she will no longer be working so hard to find the approval and attention of others, but be content with the people she has that like her for who she is, not who she pretends to be.
It is difficult for us to look past our emotions/thoughts, and step into the shoes of others. So I understand if you cannot get past your hatred and contempt. But if you can, you'll be better for it.
Somethings are worthy of malicious reaction. When one person hurts another to the point that it is unrepairable or scarring--abuse, rape, assault, etc. Or blatant malice that does great harm--notice I said "great" harm. This is like ostracizing your from your family, causing you to become homeless, taking your child from you just to hurt you (custody battles), etc. Big, life shattering stuff.
Just being a bad person, well, it is hurting herself. She needs no curse, she is living one. If it hasn't caught up to her yet, it will eventually. There is a reason for her actions, and unless she is helped, she will continue acting this way.