Your mother’s behavior could be for several reasons apart from the dementia diagnosis.  Whenever there are behaviors that are unexplained, it is imperative that your mother seeks medical attention.  It is possible that your mother has an infection or other medical condition that could be causing her change in behavior.  In addition, it is possible that your mother is suffering from depression.  Her refusal to take medications, drink or eat, as you described, puts her at risk for medical conditions, including becoming undernourished or dehydrated.  

It is important that individuals with dementia are kept active and stimulated daily.  Enrolling your mother in an adult day program or another type of social activity could be helpful.  During the day, she could benefit from participating in recreational activities and socializing with others could help motivate her to get out of bed daily.  In addition to outside programs, you can try to engage her in activities at home.  Implementing simple activities such as crossword puzzles, folding laundry, music, or cooking can all be enjoyable.  She will feel productive while also stimulating her mind and body.