I do not really know how Agatha works and if one should leave the room she appears in or it is alright to just hide in the same room's hiding spot for a while, but I am kinda glad I hadn't have to find out: Jeremiah appeared shortly after I started hiding, and through his vision I saw there was no more Agatha in the room. Another time she decided to say "boo" to me while I was passing through the entrance room. I went out, dropped off the boxes, came right in again, while she was just standing there menacingly, and I wasn't attacked.
So, I really like the fact I managed to make it in my first playthrough, without dying once. And it was before 4AM even! Either RNG was really good, or I am not half bad with this gameplay. ^^
It is a great thrill to play this game: oppressive atmosphere is amazing, characters are as memorable and wholesome as always, and the plot and happy ending are just perfect. I love it. ^^