My mum has just been told she's got cancer of the pancreas

My mum has just been told she's got cancer of the pancreas and we are finding it very hard to accept.

She has been having stomach pains and lower back pains for the last 2 months. They started mild but rapidly increased. She initially went for many blood tests but they all came back fine, except for one which was a low platelet level. We think she may have always had a low platelet level, but we are not entirley sure of that. She recently had a Ca 19-9 (i think) blood test, which was a tumor marker and is suppose to detect cells in the blood which indicate a tumor. It came back with a high level of that specific cell detected and therefore they have concluded that she has got cancer of the pancreas. We are very angry that they have come to this conclusion so quickly. After talking to our GP, we are hoping that there has been a mistake.
My mum hasn't even had a CT scan yet (which she is booked in for) and has had an ultrasound which didn't show up anything unusual.
Considering that all my mums other blood test results were fine, is it possible that she has got pancreatitis as apposed to pancreatic cancer as i have read that the CA 19-9 blood test can also detect pancreatitis. I have also read that this blood test is not really for diagnosing cancer.
Should there be any other anomolies in her other blood tests that you get when you have cancer of the pancreas. I ask this because both the haemotologist and the person who told my mum she had cancer said they were suprised her other tests were fine.

I's be very greatful for any information you have.

Thankyou