Take me or else..
So this unpublished writer works closely with well-established writer in a mentee/mentor kind of relationship and at the end of the their 6 months together the mentee is convinced a referral by mentor to her/his agent is gold.
Is it? How much influence does mentor (ie, well-selling author) have with her/his agent? Can s/he convince agent to take on his/her mentee?
An author's recommendation buys you reading time and consideration. After that your writing has to hold up.
I can't imagine a situation short of a parent/child, husband/wife, lecherous writer/nubile love object wherein an author would insist the agent take someone on. And, frankly, if an author of mine started talking about what I "have to do" we're probably headed to splitsville.
I have many people who send me stuff because one of my clients recommended them. I read their work sooner and give them more time. I don't take anyone I wouldn't have taken if they came in the slush pile. Maybe ICM can afford to carry deadwood, but I can't.
Introductions open the door. After that, you're on your own.