I, too, have been so blessed as to twice have the opportunity to meet and converse briefly with Ms. McKennitt, and I can attest that her interaction with her fans is not limited to "friends, business colleagues, and special guests".
The first time I got to meet her, I was one of the aforementioned PBS donors for whom a backstage pass had been allocated. The second time, I was merely one of the people lingering outside the venue.
She was every bit as engaging, kind, and gracious on our second encounter as she had been on our first, and after signing my program guide, and allowing me to walk her to her bus, stood patiently at the door while I stumbled through bidding her farewell.
Having had the experience of meeting her both as a "special guest" and as just another lingering fan, I have a special appreciation that perhaps no one else has sufficiently elucidated:
The meet and greet sessions with the "friends, business colleagues, and special guests" are not exclusive gatherings to which you need be invited to merit her attention.
They are, rather, obligations which she must meet before she is able to graciously indulge the aspirations of those of us to whom she has no formal obligation.
That she so freely and enthusiastically does so is measure of how well she shuns the cult of celebrity.