I feel Naomi Petit is not convincing

Naomi Petit as Mikey's Mother has some moments that stayed in my mind. The role needs more detail, but the performance stays on the surface. I do not hate it, but it did not pull me into the story. Some emotions are too simple, and I cannot believe the character enough. Many moments pass very fast, and I do not remember much after them. This is only my personal view, but the performance changed how I enjoyed the film.