Some folks feel they attract the negativists and whiners.
A person raised in an abusive situation may become overly fearful of confrontation. A bully senses this fear, despises it and is drawn to abuse the perpetual victim. Use these people as mirrors for examining your own difficult personality quirks. Try to define what it is about the behavior that is so offensive, and also consider if there is any truth in the remarks they make. She may have a clue about how complex your proposal is and is being realistic, but you may feel she is just like you mother who never felt you were as good at anything as your sister.