E-mailing a paper under review to a prospective PhD advisor; a co-author wants all co-authors to be CC-ed. Is this OK? So I am stuck in a very weird situation. I am a prospective PhD student, and I emailed a supervisor that works in a field of research very close to mine, and is very successful.
He replied stating that he is interested to have me in his team, and requested my papers. One of my papers is under review.
I asked my co-author which is my advisor for a permission, and she said it is okay to send the papers as long as I cc all co-authors in the email.
I feel like this is not a nice way of emailing a distinguished professor, especially that I do not understand the point of ccing the co-authors. I might offend the professor, which I do not want to happen.
I appreciate the advice.
I asked my co-author which is my advisor for a permission

Here a better move would have been that of asking all your coauthors for permission.
I'd now:

Inform all your coauthors, cc'ing your advisor, asking if they are OK with that.
Inform your advisor that you would not feel comfortable in cc'ing the coauthors in the discussion with the prospective supervisor.
Write to the prospective supervisor without further copying your coauthors. At most, if your current advisor insists with that, use a blind cc.