I know how you feel. My boy loves going in the car and I hate it when the end result is the vet or groomers, whom he does not enjoy! He shakes and looks so pitiful, but usually perks up when someone there picks him up.
Of course you should have left her there, she will be fine when a tech picks her up as my dog was. Soon she will be sedated and before she knows it, it will all be over and she will be back home
Hoping all goes well and she is happy again soon.