How rare is pancreatic cancer in a 26 year old female, healthy, with no personal or family history of any cancer?

Pretty darn rare. : Men over 60 and with family history and personal history of pancreatitis lead the way. Smoking is a risk factor for unclear reasons.

About 1 in 2 million: Pancreatic cancer is rare below age 50, in fact the average age at diagnosis is 71, but does occur rarely in people in their 20's- 0.4% of cases occur in people age 20-34 (but most of those are probably people in their 30's) so the overall odds are about 1 in 2 million in given year. However, having no family history of cancer makes the odds even greater for you.

Pancreatic cancer: The most well known risk factors for pancreatic cancer are smoking and alcohol abuse. In the absence of these, your risk for pancreatic cancer development is very low.