HCV induces chronic infection in 50 to 80% of cases.In rare cases infection can clear without treatment.
Most of the infected cases show minimal or no symptoms during the initial few decades of infection.
About 10 to 30 % of cases develop liver cirrhosis
over 30 years of infection and those who develop cirrhosis have 20 times chances of developing liver cancer
and this becomes 100 times more if a person drinks alcohol.
Since your sister is suffering from hepatitis C
for past 30 years and has not taken any treatment,the chances of hepatocellular carcinoma
are very high.This can however be confirmed only by liver biopsy