Most likely, there will be some amount of lip-synching.
Gaga knows that. It’s not easy to sing properly when you’re moving around dancing or contorting your body in some skin tight outfit. Ask Janet Jackson. Ask Maria Carey.
There was no skin tight bodysuit and gyrating when Whitney Houston ‘sang’ the Star Spangled Banner while a studio recording of her singing played.
https://en.m.wikipedia.org/wiki/The_Star_Spangled_Banner_(Whitney_Houston_recording)