sorry to hear that kingpinuser. i think all i can say is "thats life" man. you can only do so much to help out the people you know and love, and even when you give them the world, that might not be enough for them to stick around with you. im sure the intentions you have for this girl and her son are the best for them both, but shes always going to make decisions for herself and they might not always be what you think is best. honestly, this might be one of those situations thats just really shitty. an end to something that was once great.
going off what you wrote, this girl doesnt sounds like someone whos going to be down with you the way you might need her to be if you two ended up sticking together. im sure youre super bummed, and i know if i get bummed out on my girlfriend i can talk sort of badly about her just because im upset, so for all i know she could actually be a really great girl. but i think what you need to think about is if shes going to be a good influence on your life in the long run, and not just you being the good influence in hers. right now it sounds like shes just stressing you out, and you dont need that.
id give it a little bit of a break for now. its always really hard to make a clean break, and id never tell anyone to just drop everything and forget about the person they were in a relationship with because i know thats practically impossible to do. shit sucks man, but dont let it consume you.