Well, she should firmly assert her boundaries. Let those who modified her know that it was unacceptable. If it's a situation where she's being bullied in this way, she might consider joining a support group or getting counseling to deal with the emotional distress. Also, she can use social media or other platforms to share her story (while being careful about privacy) to get support from the community and put pressure on the wrongdoers to make amends.
She can first try to talk to the people who did it. Maybe they didn't realize how wrong it was. If that doesn't work, she should seek help from an authority figure like a teacher or a parent.
The girl could document what has been changed. For example, if it's something physical like her clothes or hair, she can take pictures. Then, she can report it to the appropriate authorities. She also has the right to demand that things be restored to their original state if possible. If it's in a social or group setting, she can try to raise awareness among others about how wrong it is to modify someone without their consent.