My biggest concern is how limited our options are if went with this school and it didn't work out.
I hear you.
Three thoughts:
1. The small gifted school seems a great match, as they moved her up a math level in just one day; highly observant and responsive teachers.
2. The kids at the small gifted school sound welcoming and approachable, meanwhile at the current school it sounds as though she has had considerable experience in "being lonely in a crowd".
3. When speaking to the current school about math options, you may also wish to discuss any possible re-entrance strategy as this may give you the "Plan B" which affords you confidence to switch to the small gifted school. (Don't burn bridges.) Even though on the surface it seems that re-entry would not be part of the current school's usual process and procedure, you might still explore arranging for her to qualify this year for next year's program, just in case you need it for any reason. The U.S. Federal definition of giftedness (as read from the
NAGC website), includes: "and who
need services or activities not ordinarily provided by the school in order to fully develop those capabilities. Your child's identification for next year's program, should she choose to return to her current school, may be considered as a service not ordinarily provided by the school, in order to fully develop her gifted capabilities.