Women who are widows are called "Widows". Women who are Divorced are called "Divorcee's". Women who are "Separated", are called "Legally Separated".
Tramps, sluts, etc., have latched onto the "Single Mom" monicker to hide their loose sex activity.
All of those you list MAY be single moms as well. I have a good friend, who is widowed, she calls herself a widow, if discussing her marital status and a single mom if discussing her parental status.