I'm going to tell my girlfriend to not dye her hair
Is there a reason that you don't like her hair dyed?
I want a woman with natural hair.
It's nice that you like her the way she is, but she's an adult and has a right decide how she wants to present herself. Doing any more than respectfully expressing your feelings about her hair and you're crossing over the line to controlling.
It doesn't matter, she cheated on me anyways.
Maybe she cheated because you were being so controlling. People don't like to be controlled by others, especially their partners.