M.W.
OK! Ummmm some of us need relaxers in our hair as Black women. Cutting it is not going to take down the volume. Actually, w/o a relaxer it's going to make it even harder to manager. It doesn't work like that for our hair texture. Especially if she has thick hair. My 7 year old has a relaxer. I had to do it at age 6...held out as long as I could. But 12, trust me, you're good! :0)
One alternative to a relaxer is the Egyptian salons. In Bolingbrook, IL there's 2. However, they are not worth the drive from WI. But I will say this, they really do know how to manage African American hair in some ways that most Black salons won't because it's too much work. They'll tell you how often the relaxer is needed and they also use some amazing blow driers that will straighten to the point where it looks like it's been relaxed. There is a down side to this. If she sweats often, that straight hair goes back to it's natural look within minutes or days. When it's relaxed, you don't have to worry about that for at least 6-8 weeks, depending on how fast her roots grow.
I hope this helps.