I think Gigi misunderstood..there is no tumor, right?
I am sorry to hear about your DD's MS signs, at such a young age..
Your Doc is probably doing the right thing, since her SX are minimal and minor. There is no cure and the DMDs are meant to keep the MS Attacks/exacerbations at a minimum and only have a 35% efficasy and may have debilitating side effects for one so young and active.
Since all other possible Diseases/tumors have been eliminated and MS is not fatal, I suggest, as the Doc does, that your Daughter live her life to the fullest and forget about the MS unless or until it raises its ugly head again.
Love and Good wishes to you..