Answer: Your boss needs to start earning her paycheck. If the daily drama is creating an office problem, then she needs to address it. These “venting sessions” solve nothing and will only make you more upset.
But if your manager remains on the sidelines, you will need to become more assertive. Dealing with this personal soap opera is not part of your job description, so when your colleague starts recounting the latest family crisis, politely excuse yourself.
Job demands always provide a legitimate reason to end conversations. For example: "I'm sorry, Mary, but I don't have time to chat now. I’ve got to concentrate on finishing this project." Keep this up, and eventually she’ll get the message.
You must also stop obsessing about her irritating behavior. The more time you spend thinking about it, the angrier you will become. So shift your focus to more productive thoughts and accept the fact that you’re working with a rather pitiful person.
For Office Coach suggestions on working with difficult personality types, see How to Deal with Childish Adults.