This is a very tough call. I have been trained as a clinical psychologist and I am very aware of all the studies and theories about therapists essentially remaining a 'blank slate', and also about boundaries between clients and therapists. There are very valid points on either side of this issue, with far fewer who believe that a therapist should disclose things in their own history to a client.
Rather than studies and theories, though, I will say what worked for me. I had worked with several different therapists over a course of many years. I had addressed many, many things in my therapy, although I still wasn't getting at the core of the issues. I was very blessed to have found one therapist that was very different than all the rest that I worked with. First and foremost, she was a very real human being with me. And I grew to trust her completely because she was open and shared many, many things from her past. I believe that there is a key component here, though, that made this OK for her to do. She had resolved the emotions around all the events that she shared with me so there was no residual energetic charge to them. I never once had a feeling that I needed to take care of her in any way, nor that the things she told me made her a weaker person. Quite the contrary! I saw in her an amazing strength and the willingness to tread into territory that no other therapist had been willing to enter with me! Frankly, I don't believe that I would gotten to the point that I am today had it not been for this therapist and her willingness to be so open and share so freely! One other thing; her work also encompassed far more than what most would consider to be 'therapy'. She worked psychologically, spiritually, and energetically, as well. When I think of 'mother' and who actually raised me, this woman is the person that comes to my mind!
Frankly, with someone who has been deeply abused in any way, they are very unlikely to really get to the core of there pain without developing a very highly trusting environment. And I believe that level of trust will not come from someone who hides behind a 'therapist' mask. In order for someone to feel it's safe for them to disclose what has happened to them and heal the root of their pain, they must have a very deep level of trust in a therapist, and that therapist must be, first and foremost, a fellow life journeyer and a real, live human being.
I'll also add that the psychological notion of boundaries are rather contrived, at best. We are energetic beings who are sharing the same source, and I would ask anyone to tell me just where they believe their boundary is!