Well, that's not accounting for ****** video quality and milisecond delay.
Because she doesn't even finish the phrase? "Ride it"... mic goes away from mouth, and the back tracking continues playing.
*click play and video will take you to the spot*, you can hear her adlibbing over the backing track. Then when she stops singing and walks over to the main stage. There's no vocals but the back track and instrumental.
Ad-libbing over pre-recorded vocals is still better than using the studio version without your mic plugged in, or using the vocals of a completely different singer, or humming off key and letting the audience sing most of the song
You don't need to see to hear her sing in and out of the song. Which is how I got that on the last video, the voice faded before the backtrack sang "...with my surfboard".
But here's a better visual I guess. It's the same deal. She sings and stops with impunity, so unless she can time every pause and ad-lib for every tour date, Drunk In Love is 100% live.