Sludge and infection treatment. Removal?

My sister, she had stomach issue and obstructive jaundice,  test was done and diagnosed with gallstone of 10mm then there was ercp done, but then stent inserted by gastro without informing us and dr is asking to get the gallbladder remove, but then she had another mri scan and ultrasound after 2 months,  where gallstone size was reduced to 4 mm and she was not having any pain, so when stent was removed, she had pneumonia and stomach infection. Stent was replaced and re inserted. After few days, she again had mrcp and ultrasound done, and found that there is cbd sludge and abscesses in liver. Can you please tell if cbd sludge can be treated without gallbladder removal? Also, if abscess can be treated now? Just to inform, she is maintaining good and healthy diet since diagnosis and no pain. However, doctors seems to be insisting on gallbladder removal, which she is not does not want. Can you please advise the reason for infection she had post stent removal?