What do you mean by slow progress? Is she on grade level? If she is on (or above) grade level, I would most likely keep her where she is. I'm presuming you had good reason to skip, and I think many kids start off slow with reading for some reason. She may suddenly take off very soon.
That said, you say the school has a high academic standard. My MG kid would have been able to easily handle a skip at most schools, but it would not have been appropriate at her gifted magnet or perhaps a private or a very high SES school.
