TNR cat—any experience?

I care for a stray cat and want to get her fixed before she has another litter. I reached out to HOPE who assigned me to All Cats Vet Clinic to get her spayed, but after reading the reviews I am VERY wary of taking her there. Does anyone know of any similar programs that you’ve had great experience with? I may just take her to my own vet, but that’s like $600 for a spay. A cheaper option is preferable, but I don’t want to take her somewhere that will treat her like trash. Thank you for any and all advice!