It's wrong to intentionally hurt someone
Gloria deeply resents a colleague she knows very well and who made her look bad in front of their boss.
Gloria wants to feel better after having been treated poorly.
Gloria decides to tell her colleague how she feels and realizes her colleague did not act on purpose, which calms her down.
Gloria uses some private information she has on her colleague to hurt her feelings.
Gloria is seen as a cool and mature individual who reacts wisely to perceived slights.
Gloria comes across as vengeful and bitter at work.