Welcome!
If you look around, you'll find that there are several threads here on MAP testing. One of the first points to note is that there are several different levels of MAP, including MPG (K-2nd), grade 2-5, and grade 6+. All of them use the same scale, but not the same material. Secondly, the percentile-for-grade-level numbers you found don't necessarily mean that she has mastered all the content expected of a tenth-grader. It actually means that she obtained the same raw score on this particular test as a tenth-grader at that percentile would have been expected to obtain on -the same- test.
Now see how these two pieces of information interact: if she was tested on the grade K-2 test, there was no material on it above about the 3rd grade level, so she was demonstrating the same level of skill -on primary grade math- that a tenth grader would. That's still a strong math performance, but not quite the same as the grade equivalents would imply. On the 2-5, it would be a somewhat higher level of math, but still not high school level.
The changes in subscores may or may not be meaningful, again depending on the content assessed. She may have maxed out some of the areas on earlier assessments (e.g., there are often very few items on geometry in primary-age math assessments, whereas numbers and operations might be expected to have a wider range of difficulty levels).
On your second question, regarding giftedness: it is possible that this does indicate mathematical giftedness. Whether this warrants additional testing is a family decision, which I generally base on two questions:
1. Is there a current problem (an apparent obstacle to healthy functioning or development) that needs additional information for elucidation and solution planning?
2. Will further testing potentially provide access to a resource of particular value to the learner (in the context of family values and needs)?
If the answer to either question is yes, then I typically would find value in further discussion of evaluation of some sort.
