If my sister has been diagnosed with celiac disease what are the chances I may have it also?

Increased risk. There is a definite increased risk if one member of a family has the disease and there are not only blood tests that can be performed but there is also genetic testing as well which can be done.
Yes & no. There are people with genetically determined tissue types that are more susceptible. There is also an increased risk that siblings will share some or all of the genes that predispose to its development. However, you can have all these factors for your lifetime & never develop it.Screening blood tests can identify those at most risk if you are concerned. Any doc can order them.