2004 Chevy Cavalier Rear Brakes vibrating Bad!!

Hi, had to use a puller to get my fiancee's rear brake drums off, (they were stuck on bad), drivers side is vibrating very bad!! Just wanted to check the brake shoes, but they were still pretty thick, now the drivers side is vibrating, when the brakes are depressed, worse at higher speed, than at lower speed. Question is, do I have to replace the brake drum? If so, Also do you have to replace both drums at the same time, and the brakes too? Or could I just get away with the drivers side drum? Just looking for the cheapest way possible right now..

Thanks,
Art Ball