You will need both her NPI and her tax ID. As far as if she is considered an individual or a group, that would depend upon how she is set up with the insurance carriers. Are all 3 docs billing under the same tax ID and group NPI? If yes, then she is part of a group, if not, then she is an individual.
She may be a group, but she is the only provider in the group. If she bills under a tax ID, group name, and group NPI, but she is the only doc using that tax ID & group NPI then she is a group, but a 1 doc group. That is actually quite common.
You need to ask if all 3 docs bill under the same tax ID & group name & NPI, or do they each have their own tax ID's, etc.
Michele