Thing to understand is that Amy's character is supposed to be unlikable.
Just like Billy Bob's character in Bad Santa was supposed to be unlikable.
I see a lot of people complaining about how awful Amy's character is and I think they missed the point that it's intentional.
The only problem with these movies is when they don't redeem the unlikable protagonist's bad qualities with sufficient redeeming qualities.
Then you end up with a movie with a protagonist who has no redemption in the eyes of the viewer. I think that's the what's happening in this movie and it tests our patience.