I'm with MCP here. It could be a dual relationship, but it may not be problematic. It seems that you'd be seeing her for the same underlying problem. It'd be different if she wanted to start seeing you for an unrelated issue (e.g., her own depression, marital issues, etc), but this seems to be something that is conceivably just an extension of the therapeutic work that you were already engaged in. There are some child/parent therapies that involve both parties with the same pracritioner (e.g., ADHD therapy with parent and child being seen by the same provider). Would need to know more details, but it could be copacetic. Dual relationships are not inherently unethical, they just increase the likelihood of ethical conflicts.