I'd love to know. I've been through 4 different tests: and ultrasound, a endoscopy, a HIDA scan and a CT scan. There was never a blood test to tell if I had stones. An ultrasound is the usual test to verify stones.
If she doesn't have pain she should pass on any surgery. There are lots of side effects (including chronic diarreah after surgery) that make it not something that should be "just done".