My Mother Is 83 Years Old. My Dad Died From

My mother is 83 years old. My Dad died from pancreatic cancer a few months ago. They had been married 63 years and they were truly soul mates. Dad was from Tennessee and Mom was from Arkansas and they both joined the Marines and met at the base in San Diego and got married a few months later. I was born 14 months later after that. Mom went for her yearly check up yesterday and her Doctor who RARELY EVER prescribes medication did prescribe Celexa. We are wondering what the side effects are and if she should even start taking it. I live within walking distance of her.