How do I know if my mother is depressed?

Depression is tricky and needs to be diagnosed by a doctor. If she has little interest in life events - especially things she used to find important - that is a clue. If she neglects herself, sleeps too much and is sad a lot, she may be depressed. However, some symptoms aren't so obvious. if you think she may be depressed, please get her to a doctor.
Good luck,
Carol

What if she has been on an antidepressant for sev. years yet her symptoms are getting worse, what then?

Some antidepressant medicines can stop working with in the brain on some people. The body cam grow immune to the medicine, I would suggest you speak to your mother's physician and let him know of the changes in her and let them be the deciding factor if something needs to be done with a medicine change.
Blessings,

Bridget