I once knew a wonderful elderly minister who said that we could take a lesson from the Rabbi in "Fiddler on the Roof" in that there is a prayer for everyone & every circumstance. There are usually folks into "prayer" at most every place of employment. You might ask them to pray (or do it yourself) when in earshot of the colleague:
   God bless Ms. colleague, & keep Ms. colleague--FAR AWAY FROM US/ME!!!   
    OR, let Ms. colleague know that you have become a student of, say, Positive Thinking, by Norman Vincent Peale, (or perhaps some well known motivational speaker, and your assignment for this month is to keep a positive attitude & see your place of employment only in a positive light, which is very difficult since, poor dear, she seems so unhappy,so could she please confine her comments to positive statements.   And would she, dear friend, like to read some of the positive thinking literature?   If you need it, you can often find a copy of The Power of Positive Thinking in many thrift/2nd hand stores to give to her--or to read for yourself.
      Most likely she will run for the hills when she sees you coming.       Good luck.