When I first saw this it bugged the S*** out of me, I don't know if they explain it, or if i'm just missing it, but if the mom hasn't seen Mo or Meggie, how did she know what they lookd like? I remember (unless i'm crazy) the drawing was the same as how they looked in the movie....
shareShe knew what Mo looked like, she was married to him. 9 years is a long time, but I don't think she'd have trouble recognising him.
In her drawings her daughter was still a baby, like just before Resa got sucked into the book.
If you mean how she recognised Meggie, Meggie was with Mo when (Resa saw them both at the same time), she was the right age and probably looks somewhat similar to her toddler self.