I do not believe anyone who has not hired that particular therapist to act as a therapist would know whether they were a good therapist or not. Being a not horrible colleague is not, to me, the same as being a not horrible therapist.
No one would know that I hired a therapist or who that therapist was by name. The other person I knew who also hired the woman had a different experience of her than I did. Even if I heard someone say the woman was a good therapist, it would not have any bearing on me one way or the other. For me, I would not see it as validating in any way.