Obviously, she has no tolerance for this poor defenseless pup. Maybe instead of flipping out on her, you might try to get to know her and see if you can intervene somehow. I know that is a difficult thing to do because I am with you...I would rather smack someone down for being abusive.
The problem is that no one will do anything ... if she left the pup outside with no food or water you might have a chance of something being done.
She sounds like someone who might eventually turn that pup into a shelter after she has totally destroyed it's spirit...I would do my best to get to know her and try to get the poor thing away from her nicely.
If all else fails....put dark glasses on and drive a car with no license plates.
And, I am not suggesting murder here.