I dont think I would allow the change. MDI seems easier I know, but one loses more control. Here is what I would do, I would explain the pump is a big investment and it needs to be used. If it is a medtronic let her personalize it with stickers etc. I love the skins, I use them when I get tired of mine.
If she were to go on MDI be sure she checks more. I would raise the testing regiment to reflect the loss of control.
She likely wants to go off for two reasons.
1. others kids dont have them, I get that. it is tough to be 8 and different especially if boys are being noticed. Help her figure out ways to explain it remember she can blame wearing it on parents. (My mom and dad make me) as parents we have big shoulders and can carry that burden and
2. she likely felt MDI was easier. Likely because you had more of the burden, if she does go back to MDI, I would push some of that burden over to her. Hey there is a cost for everything and as humans we usually figure out the least costly path.
I do know a kid about her age who has been on and off four different pumps, because none suited him for one made up reason or another. He wants what he does not have and as a parent if I let her go back id be pretty stern about responsibility, she might find she likes her pump.
I think (but dont know) this is more about other kids than her. Not being different is a big big issue at 8 years old. I would also call a school counselor, principal, nurse or social worker. They may have some ways to help out.
I just never let my sons out of things very easy. I always tired to make sure there was a cost not in money but in other ways. I would do the same here. Just me of course