It's Not Custard.

It's Not Custard is the darkly comic story of Louise, a teenager suffering unrelenting acne and continual bullying, at home from her cruel older sister Jennifer, and at school from tormentors in and out of class. She wishes to cease their teasing and she is presented with such an opportunity when she awakes to find her acne gone. However, this magical gift has a bizarre consequence...and it's one that favours our hero.