(MRIs cost a lot more than ultrasounds; maybe she was less money-hungry than you think.)
If you think there is fraud involved, contact the medical review board. Cervixes don't prolapse, uteruses do, but since the cervix is simply the end of the uterus, maybe that is what she meant. If she thought you had a prolapsed uterus, I'm a little surprised she didn't order an MRI, since it shows soft tissue and an ultrasound doesn't do that so much. But I'm not a doctor and would be glad to be corrected on any of these remarks. :)