What can I find for my 97 year old mother to do?

In the past two weeks, she has been sleeping more and more. She just seems depressed all of the time. Yet, when I ask her if something is wrong, she always mutters, no. She takes celexa. It has worked in the past, but doesn't seem to. We want to keep her at home with us. I can't just leave her at an adult day care center, because she is wheelchair bound. The last one I tried, just left her parked in her chair all day. Please, please help me.