what can cause recurrent gallstones in the bile ducts n liver every yr when gallbladder has been out for 20yrs?

its been happening every year on the dot pretty much the last 3-4yrs.my mom got gallbladder out when shw was like 20 or so so almost 20yrs.her symptoms are extreme cramping in upper stomach so bad where it makes her vomit really hard,nausea and if she gets anything on stomach sometimes as little as some water will set it off! her prescription for lorazapam helps some though.really wanna know what can prevent this maybe cuz she has no insurance so we cant keep going to hospital so am hoping once this is gone we can prevent it so we dont have to worry about this no more! her last gi doc cut her bile ducts open some so that itll help stones come out easier but now its back again :- thanks have a great night everyone! :-) <3