We switch from Elly feeling annoyed to Annie wondering why Elly thought she was irresponsible.
Panel 1: We start off at Annie's house; as Annie hands Lizzie over to Elly, she explains that Mike came home right after school just like he was supposed to; he then fed and walked Farley.
Panel 2: She then says "Elizabeth was such a good girl; she are her lunch, had a nice nap and played well with Christopher."
Panel 3: As she gets ready to leave, Elly says that Annie's a sweetheart and she's grateful to her. She does, though, feel guilty for leaving her children with another mother. Annie asks why that is.
Panel 4: The reason Annie is confused by Elly's guilt is that not only does she get paid to do something she loves, she gets thanked for it.
Summary: The point I think Annie was trying to make was that she can't understand why Elly would feel guilty about doing something that would earn her some spending cash. After all, she's the one who came up with the idea in the first place so the end result isn't going to bother her, right?