If you wish to follow traditionally correct English grammar, you should probably answer: Yes, this is SHE.
a. This = subject
b. is = linking verb
c. she = subjective complement. (You need the nominative case after a linking verb, NOT the objective case "her.")
In reality, however, probably most native American speakers say "her."
If you say "she," some people may think that you are being snobbish, and some people (who do not know the rule) may think that you are speaking "bad" English!