You are wise to turn away from this woman's malicious gossip (for that's what it is). By giving her an audience you'd only be encouraging her, and you might also be poisoning your own mind and heart. The Bible says, "A gossip betrays a confidence; so avoid a man (or woman) who talks too much" (Proverbs 20:19).
Why do some people act this way? One reason, I'm convinced, is because they think it makes them better than other people. In other words, if you tear everyone else down, who is left standing? You are–and it makes you feel superior to everyone else. Behind this is pride–the kind of pride that says, "I am better than you are."
But this attitude is wrong, not only in the eyes of other people but also in the eyes of God. The Bible warns, "Pride goes before destruction, a haughty spirit before a fall" (Proverbs 16:18). It also declares, "Whoever slanders his neighbor in secret, him will I put to silence" (Psalm 101:5).
Pray for your fellow worker; down inside, she actually may be very lonely and miserable. But whatever her feelings, ask God to convict her of her sin and help her turn from it. More than that, pray she will realize God loves her, and wants her to discover His love by giving her life to Christ. Yes, avoid her gossip, but ask God to help you point her to Christ.