Well, if she doesn't have hepatitis C, this is already good news. I am sure her doctor will find a reason for low platelets. Sometimes immune system destroys them, or low count can be a reaction to some medication.
Thrombocytopenia has multitude of causes. Your wife's doctor will look at her history, symptoms, and lab work to determine what is causing low platelet count. It is not possible to make any conclusions over the internet without knowing details.
Low platelet count definitely needs to be investigated.
Does she have Hepatitis C. This forum is for people with HCV.