I doubt she was lip syncing. Just observe her chest cavity and her posture. She isn't straining because she is singing correctly and she is a soprano so those notes are very well in her range. She is holding still with that awkward position to make sure nothing interferes with her breath control and that her head voice is well-supported. She even licked her lips at some point because her mouth was probably dry from singing so much in her head voice as.
If any of you sing, I'm sure you could back me up.
thats true, and you could also see the veins in her neck almost popping out. if shes lip syncing then she must be an alien or something cause you cant have popping veins like that without creating any vocal sound.
She's definitely not lipping. That's how you're supposed to sing when you sing opera. Open-throated and full-mouthed. (That sounded dirty.) And she does it flawlessly.
That was Andrew Lloyd Weber in the beginning of the video so hardly "community theatre". Educate yourself and know your place because neither of your faves will ever be able to sing like that.