Question

add question tag to
1) she is an excellent dancer​

Answer 1

HEY MATE
HERE'S THE CORRECT ANSWER

She is an excellent dancer, isn't she?

Answer 2

Given that “she is an excellent dancer​" and you have to change into question. Here answer is isn’t she? It is right answer.

When the given sentence is in the positive, you need to go add not in the question tag else if the sentence is negative, then you should not add not when come to write the question tag.