I'd call a widow unmarried if she wasn't currently married.
I suppose the language usage might get complicated.
Is she still a widow, in the present tense, after she has remarried? Looking at a few definitions, it appears so, but the archtype of widow is one who has yet to remarry.
http://www.scientificamerican.com/article/rational-and-irrational-thought-the-thinking-that-iq-tests-miss/