Cancer/legal question

[winneythepooh7]

One of my friends who works in a high-powered consulting job in the DC area has a history of cancer, and it seems it may have come back. She has had problems with the company she has worked for before making it "difficult" on her if she is out here and there for doctors appointments. Can a company legally fire someone for this (or realistically, find excuses to get rid of her)? She needs the health insurance obviously with everything going on. There are several employees in my agency that have cancer and some who have passed away unfortunately and the agency understood and worked with them, even when they weren't doing well or needed to be out for their cancer treatments. But then again I work in Social Work and Mental Healthcare so it is a completely different view towards employees who have personal/medical problems. Any recommendations/advice will be helpful.