I feel for your grandma because she is in a tough situation, but isn't it also plausible that someone in your town could go to Omaha for medical treatment, or on business and get infected and then infect her at the local grocery store? Nearly every county in every state has had positive cases...i'm guessing the county your grandma lives in is not completely free of the virus and someone that doesn't travel to Omaha or a football game could also infect her.
Do you think the chances of getting a virus are the same if you walk by a guy on the street as they are from sitting with 90 thousand people in a stadium?