Dandylin, sounds like you are expected to be a caregiver too at work. Hope you get some understanding from the boss. Maybe sales reports would speak louder than griping.

I feel sorry for the coworker, but it sounds like she is having trouble coping with work.

If you are like a supervisor to this coworker, maybe you could ask the boss to administer to her so you could focus more on sales. Sounds like communicating to the boss without being a pain is important to maintaining good relations and your job.