How can I support my son's grieving firstmom?

Hi all, I haven't been on adoption.com in a very long time, but the knowledge that there are some wonderful firstmoms here who may be able to give me some advice has me back. A little background: My son was born in 2005 to a wonderful woman, S. She contacted us about 6 weeks before his birth wanting to make an adoption plan. She wanted a closed adoption, and we really wanted an open adoption. We moved forward together with the understanding that my partner and I would always be open to contact and we gave her all our identifying info so she could contact us in the future. S chose not to see our son when he was born. She lived in our area for the last few weeks of her pregnancy (this was her wish) and then moved back to her hometown. She had planned on not telling anyone about her pregnancy, with the exception of one friend's mother (Z) who was helpful to her in discussion options for her unplanned pregnancy. She also refused the conseling offered to her during those weeks before giving birth. During this time my partner and I had gotten to know Z, and after our son's birth we sent pictures and email updates to her. S decided to read/view these -- I can only assume that it maybe gave her some measure of control to access these on her terms on days she felt up to it? Anyway, through Z we let S know when we were visiting relatives in the area when our son was 15 months old and S jumped at the chance to visit with us and meet her son for the first time. That was obviously a very emotional meeting, but we left thinking that our adoption was opening and we were very excited about that. S had mentioned being open to increased contact, so we called her cell later that week and it was disconnected. Emails to Z started to go unanswered shortly after that. Fast forward to now -- this Christmas on a whim I sent an email to Z giving a little update and she wrote back! She also gave us S's cell number. My son turned four on Thursday, so my partner and I finally worked up our nerve to reach out to S again and called her on Wednesday night. S was fairly thrown to be hearing from us, but said she welcomed the call and that she missed us, etc. My partner talked with her Wednesday night and I talked with her the next night (I'm always the one who makes her cry... I think she wasn't ready to talk with me the night before). It was really, really wonderful to connect with her. She's doing very well -- in school full time -- but it's also very obvious that she is really hurting about her adoption decision and doesn't seem open to getting counseling or support. I've mentioned webboards for birthparents (she's not really online right now), or getting counseling, or maybe even journaling (she's an amazing writer), but she sort of brushed aside those ideas. Still, she says she's built up a lot of walls over the past few years and has a hard time reaching out to others. At some point her mother guessed about the adoption (most people still don't know) and it's pushed them apart some as well. I want to be helpful -- S has requested new pictures, which I am ALL to happy to provide, and I'm going to continue to reach out to her since she seems to really value the contact despite not wanting to initiate it. I asked her if I could call her next week and she was open to that and seemed excited about continuing to talk. I can keep suggesting getting some help for her grief and loss... but does anyone have any other advice? I don't think she's (currently anyway) wanting contact with our son, and as of yet he hasn't asked to speak with her -- though he knows we've called her (I think most four year old boys have zero interest in talking to relatives or other adults on the phone!) and we talk about her and his adoption story regularly. I really care about S and want to be supportive. I also recognize that adoption is a multilayered issue and that there's loss involved and don't feel threatened by her grief -- I just want her to not be battling depression and be there for her so she can heal as much as possible. That said, I am probably not the best choice for her to talk with about these feelings -- I'd imagine talking to the amom of our child about how you are sad/regretful/whathaveu about your decision to place probably isn't the "safest" place emotionally to work through or with those feelings. Anyway, advice is welcome. Thanks for reading my novel!