You have not given details of the test, which has found traces of the bacteria in her blood. Most likely this would have been the widal test and not blood culture (which detects the presence of live bacteria in the blood, and is a direct evidence of infection) since it is practically impossible to have asymptomatic bacteraemia in typhoid.
Widal test on the other hand is an indirect evidence of infection and looks at antibodies against the salmonella bacteria, and this can be positive either during an active infection, after an active infection, after immunisation or due to an anamnestic response to an unrelated infection. Therefore interpretation of Widal requires clinical correlation as well as repeats titres for confirmation after 2-3 weeks.
However, in your sister's case, you do no need to worry if she has been adequately treated with antimicrobials against the bacteria for a sufficient time period according to the sensitivity pattern.
The only precaution that should be taken is to get an abdomen ultrasound to look for gallstones to check for biliary carriage. A Medical specialist is adequately trained to manage typhoid fever, though if an infectious disease specialist is available you could consult him.