My girlfriends children treat her and lately me like crap ..details below.. what should i do?

me and my girlfriend have been together for 10 months now and i knew i was in love with her from the very beginning.. she has 2 boys 12 and 13.. i didnt meet them right away because i wanted to make sure we would work out before i came into their lives..because i know from experience (my dad dated many women when i was growing up) that its not right to bring people in and out of a childs life.. anyways i met her children about 4 months ago.. they have always gotten smart with her and treated her badly.. and at first i let her handle it because its not my place and i wanted them to like me and i had hoped that maybe if i formed a sort of friendship with them at first that maybe i could get through to them one day.. you know, have a heart to heart and tell them about my experiences growing up, and that their mom does everything to try and make them happy, life is short etc etc.. anyways.. her kids are pretty out of control.. the youngest one has pulled a knife on his brother and has extreme anger issues.. and the older one was just expelled for bringing a knife to school.. and hes the better of the 2.. so that was sort of a surprise.. they both just walk all over her.. and are spoiled brats.. i try to help her figure out a program or something for them to help with their attitudes.. they expect to get whatever they want.. and she usually gives it to them.. i tell her thats not the way.. but since i dont have kids i think its in one ear and out the other.. anyways about a month ago.. she took the tv and xbox and phone away from them for acting up.. the youngest one pounded on her door while i was there and demanded to get it all back.. she told him no that he was being punished.. he then began breaking things and throwing things at her door.. i told her she should call the police because its really gotten out of control.. so i guess he heard me.. he called me a "fat b****" i was so shocked.. guess i should have seen it coming.. but they dont cuss at her even when they act up.. i ended up leaving that night without really saying anything because i thought i would lose it and end up in jail honestly for ringing his neck.. she got mad at me for leaving.. but after he said it.. she didnt say anything.. im sure she was mortified.. but i feel like she should have defended me.. we stayed together and i just ignored him.. which i dont think is right but i didnt know what to do.. i wanted an apology and she told me he was scared to apologize.. so i gave him a month.. and now hes back to the way he was.. he doesnt talk to me but walks around like its his house.. and i feel like it was just let go.. and i cant move forward.. i asked her if he was gonna apoligize and she got angry with me because i bring it up all the time.. i just feel like if she cared like i did she would have made him do it.. he doesnt even have to mean it.. i just feel like if he was embarrassed having to say it to me face to face he would change knowing there were consequences for his actions.. also.. last week.. he was yelling at his mom again and i couldnt take it so i snapped .. he was askin her to take him somewhere after she asked him to help her with something and he wouldnt do it.. i said "do you really think shes gonna take you anywhere when all you do is treat her like crap, maybe you should start respecting your mom and everything she does for you and then you would be able to go places!!" i just wish they would see that if they would act right we could go play lasertag or anything you know.. or not even that. i just want to get along.. i feel bad that i lost it.. but then it made me think.. dang.. im willing to defend her from her own children and she wont defend me from them.. she spoils them and they take advantage.. she struggles just so they can have nice things and they dont care.. they act like they are the adults.. asking her questions that no child should ask a parent.. like "what did you spend your money on" when she says they cant eat out.. i dont get it.. i just love her so much but it seems like shes not trying.. its hard to get them into programs because they are expensive and she doesnt make alot of money... she grounds them but then when they get on her nerves asking for stuff she will give it back.. i just dont know what to do anymore.. i feel like i deserve an apology and they feel like they can do whatever because she lets them get away with everything.. we are on the verge of breaking up.. i wish she could just see that im trying to help.. any suggestions?? she hates when i bring up the subject but will tell me things they do and it drives me crazy.. if i wasnt so in love i would have stopped seeing her right after i saw the way they work.. i thought i could help.. not that it really matters but im a woman (30) shes (34) they said they were ok with us being together from the beginning but i guess its changed because im not puttin up with their crap.. please help