How does 'Ask to watch kids' work?

[Dullahan]

I have a mother and her child daughter living in an apartment. The mother leaves for work at 3pm, so she needs someone to watch her kids. I asked her neighbor to, and she agreed. But as soon as the mom left, I got a warning that said "It's not a good idea to leave Haruna alone without supervision."
The neighbor was in her apartment unit, whereas the child was in her own. Do they have to be in the same unit, or what? Because I can't get it to work.