Demotion with no reason given

I was recently told that a Program Coordinator from another of our company offices would be replacing me (I was the Program Coordinator in my office). I was told this decision was because I was going through so much on a personal level. I was shocked. I had confided in my boss that my husband was diagnosed with prostate cancer and that we (my husband and I were going through bankruptcy). I could not believe what I heard because I had not taken any time off over anything I was going through. I have never been written up or talked to about anything. Quite the contrary. My boss always told me and everyone else in the office during meetings, etc that I was a godsend to her. She often said that she had been praying everyday for someone that had her work ethics and dedication to come along and then I came along. She says "God answered my prayers when Maria came to work for me." Now, after 5 years, I have been demoted and a person who has not been there as long as I have, and was my bosses roommate, and a who is a dedicated member of a same group (NA)as my boss has my job. At the same time that I was demoted, someone in my office got fired and I was put in her place.

I feel that this person was given my job due to the close ties she and my boss have, not on the effectiveness of her job (she has had complaints filed against her by fellow employees and clients). Do I have grounds for filing a discrimination lawsuit for favoring personal friendship over quality of work?

Also, when I asked my boss to clarify what she meant by the fact that she did this because of all that I was going through, she apologized and said that she never should have said and that she said it because she did not want to hurt me. I have no idea what she meant by that. What I do know is that my work has been top quality, I do not take time off work, and I do other peoples work when they are not there.