Hi,
Welcome to NT.
I was told exactly the same thing they told your DD. Live life and don't worry. That was 30 years ago, what else could they say? But you know, it is true. She may never have another attack ever. Some people live to a ripe old age and never have any more problems. It was just the lesions in the brain and a few minor symptoms, that may go away.
How is your DD doing? Is she upset? Why were they doing the MRI looking for that pituitary tumor? Is she diabetic, have growth problems, female problems? There are so many diseases/disorders out there. I am sure they will find out what her problem is soon enough.
Early treatment for MS has not been proven to be worse than later treatment, or even none at all. She is young, if she is not having other problems then give her time to be a teenager, graduate, go to college maybe.
I wish her well. Even with the lesions she could be fine. Nice to meet you and good luck.