[in] Neighbor's 12 Year Old Child Keeps Running Away To My House. She Wants Me To Lock Her Child Out When This Happens. Do I Have To Comply?

My neighbor adopted a girl several years back (I think when she was 7 or 8) and has been locked in a power struggle with her ever since. It got particularly bad last year, my neighbor would try to confine her to her room and she would break out through the window and run away to neighbors' houses - like mine. The neighbor and I were friends before this started happening, and we even hosted her birthday party at my house one year so the daughter sees my house as a safe and fun place.

The last time this happened, I did what I usually do which is to text the neighbor, tell her that her daughter is safe with me, and that she should come pick her up at her earliest convenience. She responded to me by saying NO, I shouldn't have let her into my house, and that I need to send her to walk home (in the dark) to her own house several blocks away. I refused saying that I didn't feel comfortable sending a young child out in the dark by herself. After a protracted argument she eventually relented and came to pick her up.

Flash forward my neighbor apparently sent her to some kind of facility for the past year, and now the daughter is preparing to return home. In anticipation of a repeat incident, my neighbor sent me a very strongly worded letter saying that I am not to have any contact with her daughter. I don't believe this is enforceable (wouldn't she need a restraining order?) and also I feel like it would be irresponsible and possibly illegal to comply with the neighbor's request should the child show up on my doorstep again in the middle of the night. From a legal standpoint, what am I supposed to do if this happens again?