It sounds as though your gf has been having a really tough time. And if her DS has had her in tears, I would say that she might welcome some gentle assistance. Perhaps you could suggest she contact PPP to see if she could get in for one-on-one sessions or something like that. Or maybe you could attend a group class together so that she is not alone. There are a few programs like that, and it might really help your gf. They would also be able to advise whether or not the DS might need further assessment.

In the meantime, books such as Toddler Tactics by Pinky Mackay have some great tips for handling toddler behaviours, as well as some insights into what causes them.

I know you are worried about your kids also - it might be a good opportunity to explain to them why the behaviours they are seeing are not acceptable. I am sure they will be able to understand why it's not ok to copy.

GL with it hun, it's not an easy situaiton. You are a great friend for helping your gf out when she needs you most.