Talk to other clients if you can, find reviews of the service on the internet, and in general, just learn as much about the general clientele as possible. In particular, ask how many short-term repeat customers the matchmaker gets. For a matchmaker, a high customer short term return rate can mean a number of things, including that (a) many of her customers are merely in it for the chase and not the catch, or that (b) many of her customers simply don’t play well with others. Neither quality speaks well of the matchmaker. Also keep in mind that a lot of matchmakers (particularly the really expensive ones that position themselves as matchmakers for “mature successful single professionals” are really just meat markets for wealthy people who want expensive flings.
Additionally, read the service contract if you can. Good ones will contain explicit compatability guarantees, indicating that the service really does its homework in selecting matches. For example, if your friend requests in her initial interview not to be matched with any Furry fetishists, she should be able to refer to the compatibility guarantee in her service contract when asking for a refund the morning after being chased around by six-foot tall horny squirrel.
Of course, this is all from my limited experience. I was in your position once, relative to my mother. Not in that I went to the interview, but just in that I reviewed the contract and eventually got involved in a dispute with one of these companies. My obligatory anecdote:
My mother is a widowed, early 50’s, 5’8", 125lbs, attractive, physically fit, professional with postgraduate education and a nice salary. She’s not wealthy, but she’s comfortable. She used a service in the Philly area one time, just to see what it was like. She paid $2,000 for three dates, on the promise (written in the service contract) that the matchmaker would pair her with men who fit her desired profile: 50-60 year-old, taller than she, well-educated, financially independent, Catholic, healthy, physically fit skiers interested in possible long term relationships.
Her first date was a short Jewish man who, while he had about a million in the bank, also had an extra hundred around his waist. He hated the outdoors, and he’d never been skiing in his life. My mom complained to the service and was given an additional match at no extra charge.
Her second date was a 60 year-old Catholic who had quite a bit of money, was an accomplished dancer, very well-cultured, and in very healthy physical condition. They had a pretty good first date. For their second date, however, he invited her on a romantic weekend vacation in Europe. She responded that this was a little too fast for her taste, at which point he confessed that he had used the same matchmaker more than a dozen (that’s $24,000) times in the past year to set him up for what basically always amounted to weekend long flings with no strings attached.
It was at this point that, entirely at my mother’s request, partially in my capacity as a concerned son and partially in my capacity as an attorney with a penchant for writing threatening letters, I convinced the service to give her her money back.