That's her character, not her. She's playing a late twenties, jaded New Yorker as a generational contrast to her two costars' characters. If you happen to subscribe to Disney+, check out her performances in the TV series Wizards of Waverly Place. She was wonderful in that, and often stole whatever scene she was in. BTW, that series appeals to adults, not just kids. Somewhat unusual for Disney.

Selena Gomez is doing fine after Disney and I'm looking forward to her new projects.

@dawna3 said:

This is my first time seeing Selena Gomez in anything and I just find her a bit….odd. She speaks with such a stilted voice, like her jaw is locked or something. It’s just an odd way of speaking and I am not sure if she’s doing it for the character or if this is natural for her. It’s nasally or something.

What do you all think?

I replied earlier, saying it was her character, not her. But after hearing a recent interview, that appears to be her natural voice: usually a monotone.