They are doing an impressions game it's not like Xtina is mocking Britney so I dont get why X is being shaded and vice versa. Im sure even Britney would love that her childhood friend doing an impression of her and a spot on one at that.
Exactly, it's all in good fun! Here's Adam Levine & Jimmy Fallon playing wheel of musical impressions for anyone who is unfamiliar with the game... Xtina does not choose the artist/song https://www.youtube.com/watch?v=zCbfWGgp9qs