I don't believe that sugar will stay for 2 years in your system only if, you taking soft drinks everyday. When you drink soft drinks, remember you are drinking sugar at the same time. People can get diabetes for too much sugar intake, alike what your mother do, drinking soft drinks just like water. This is the bad sign of developing diabetes in a long run and added to it if you have family or relative that develop such disease. My late grandad died from complication of diabetes, there is no cure for diabetes, you just have to control it and strick discipline in taking foods.
Remember,if you drink soft drinks everyday, that's the reason why it will stay in your system.And too much sugar, our system cannot handle it. You need to drink 1 Liter of water for every 1 cup of soft drink you take. This way,your body will eliminate and cleanse your system by peeing every now and them. But,better to avoid drinking soft drinks because it's not healthy.