You shouldn't be concerned with who your ex dates.
Hannah's friend Julie called her to tell her she has a date tonight with her former boyfriend Thomas and wants to know if she had an issue with it.
Hannah wants to react to Julie's date.
Hannah tells Julie that the past is the past and to have fun.
Hannah immediately says that Thomas is off limits and slams down the phone.
Julie goes on her date with Thomas and has a great time which makes Hannah happy for the new couple.
Julie doesn't go on the date with Thomas but it causes a rift in her and Hannah's friendship.