Nothing really special:
Delay, reverb, chorus, compression and a number of voices singing unisono ( quadrupled, rather than doubled lol..) + choir.
Maybe some minute pitchshift up&down on the doubled voices for fattening, perhaps (or shall I say most likely) Melodyne ....
Basically, anything that makes a thinly voice bigger and gives it the power to be heard in a dense mix.

Sorry, I didn't see...
Welcome to our Recording Forum, Ken!!

Hi Ken welcome to RO.

I wouldn't assume everything you're hearing is technically being performed live either.

Backing tracks = the dirty little secret of many big acts. Not necessarily lip-syncing - but singing along with studio tracks.

Yeah Shes singing with the backing tracks Theres at LEAST three more of her as well as the backing vocals and the LIVE backing vocals. Also theres a crap=load of backing instumental tracks. She is doing a really good job of it however as this isnt as easy as it looks. Real trainwrecks happen when they CANT perform their songs to some degree.