HELP PLEASE!! Unbearable situation with Mother-In-Law?

I just posted earlier today about my enfuriating (soon-to-be) mother-in-law, and something else just happened that´s made me really mad....Basically Im from a Western country, but im living in a latin american country where everybody lives at home till they are married...which means that even though my boyfriend is 29 and I´m 27, and we´re planning on getting married, he STILL LIVES AT HOME. Ok, I can handle that, although it is definately strange for me after having lived with boyfriends in the past..But sometimes I feel like I am back in high school again....Anyway, i get along really really great with both my father-in-law and my sister-in-law, and even though I still cant speak the language completely perfectly, they are always patient with me, and laughing along with my mistakes and stuff......Then there is my MIL. We never really clicked, as she is a very traditional, small-town kind of lady, and I dont think she was ever thrilled with the idea of her son dating a "foreigner". But I always made an effort with her, and we had a courteous, if not warm, relationship. But now that it has been made clear that we are going to spend our future together, I think this has really hit her hard...not only is he going to move out of her home, we are also going to move together to my country, and she sees me as the ENEMY. I can understand those feelings of anger, maybe jealousy and loss.......BUT I just cannot understand the way she´s started acting with me. Over the last few weeks, she has blown up in my face and started shouting at me over the most absurd and ridiculous things, and outright insulting me. I am a very very calm easygoing person and always try my best to get along with everyone....but this was just the last straw. I shouted back until my boyfriend heard us and came running in to my defense and completely put her in her place. But since then we haven´t spoken, and I spend a lot of time at their house, so it is really uncomfortable...I just spoke with my boyfriend who was on the way to get me, but his Mum had grabbed him and said she didnt want him to go see me, I had "changed him", and that I was "a #@€~€¬" etc etc.......I am just absolutely horrified by her behaviour...I have never done anything wrong by her nor been anything other than the perfect DIL (I even made her breakfast in bed on her birthday when none of her family did anything)....I know that it is not exactly ME, as opposed to what I represent, and she was like this with ALL my boyfriends past girlfiends...but HELP!!!! What do I do?? Now she is painting me out to be the bad guy and I havent done anythng wrong....I know some people will suggest sitting down and talking to her, but she is not the type if you know what I mean - she is an Alpha female and what she says goes.....Any advice would be really really appreciated right now