What can I do when my mother has depression and cries every now and then?

If you haven't already I would have her seen by a geriatric psychiatrist. There are medications that can help to stabilize her moods, do this for her sake as well as yours as she must be in misery. If she is already on medication that isn't helping others here have mentioned that a short stay at a psychiatric hospital can help to get medication issues sorted out.

Get her on some calming medications. Call the MD.

what do i do when she wakes ups and does not sleep and I need sleep because I work she crys and screams