It's rude to tell someone they need to lose weight.
Andy hasn't seen his sister who has gained weight in a while.
Andy wants to tell his sister how she looks.
Andy tells his sister that he noticed she had her hair done.
Andy tells his sister that she is fatter than the last time he saw her.
Andy's sister is excited and tells him the name of the salon where she did her hair.
Andy's sister turns around and walks away, completely ignoring him.