Ending a Coaching Relationship

My daughter referred a friend of hers to me who was interested in becoming a Life Coach. I did an initial call with her, and offered to mentor her as she comes up in the field. She decided not to pursue certification via LCS, but through an alternate program. We stayed in touch and gradually it seemed that the models she was sharing with me were more personal than professional. I still felt comfortable and gratified that my training enabled me to address anything that any client presents. Now this young lady has moved back to the same city as my daughter and is dating and interacting in the same friend group as my daughter. The models that she sends me include people I am familiar with and I feel uncomfortable because my thought is: I know too much and I am too close to be objective and helpful here. How do I best communicate that I would like to end this coaching relationship in a clean kind way?