Thank you for your patience in my response. Also, thank you for your question.
We don't have information on mentoring for birth moms in foster care specifically, but Chapter 22 of the Tool Box has several different sections on youth mentoring. See https://ctb.ku.edu/en/table-of-contents/implement/youth-mentoring. You may also want to do a search of various mentorship models that you could use that fir what you are doing.
It also sounds like you may be working with a fairly vulnerable group, correct? I may also consider thinking about creating a coalition (of sorts) to assist in addressing this topic. See Toolkits 1 https://ctb.ku.edu/en/creating-and-maintaining-partnerships and 2 https://ctb.ku.edu/en/assessing-community-needs-and-resources. A coalition would bring together different stakeholders that have a "stake" in this topic, such as local community members, health systems, and the foster care system, for example. I understand that this is far beyond what you are asking. And, by converging a group like this, you may also gain access to these important resources (and knowledge of them).
Thank you for writing in! And, good luck with your important work!