Need advice, I'm srsly about to go crazy!?

Alright, back story:

My bf bought me a plane ticket to South Korea to meet his parents (we've been dating for about a year).

I really really wanted to go, but my mom hates my bf and is afraid of something "bad" could happen to me in South Korea. Sooo my plane was supposed to leave on Dec 27th...And...I was about to walk out the door with everything, but she physically stops me (punches and pushes me) from leaving!

Soo now I feel terrible and my bf and his parents are really disappointed. And I have an un-used plane ticket that I have no clue what to do with.

The thing is, I have the option of going to South Korea January 2nd to the 19th, even though it will cost $800 extra to change my ticket. My bf's parents are willing to pay this and I really want to go.

Now, before I tried leaving THE FIRST time for South Korea, my mom told me if I don't go and stay here, then our relationship will get much better and she'll be nice (my relationship w/ my mom has honestly sucked for the past 2 years). So anyway, I stayed (reluctantly) in America when I was supposed to leave...Then THE VERY NEXT DAY my mother starts ranting and raving and going crazy (as usual, no lie) about how stupid i am and how she wants to "take a step back" from me. And she's now going to move out of our apartment, let me take over the rental-lease, and move somewhere that I won't be able to go cuz she willingly will not tell me where. She doesn't want anything to do with me anymore. BUT WTF its like, she promised me to change if i stayed (and i did, even if i was FORCED to stay) but then she doesnt change??!?!?! What am I supposed to do?

Also, if I go to South Korea, my twin sister would be INSTANTLY kicked out of the house...But now im thinking "well that doesnt matter if me and my sister will have to take over this rental of hers".

(My sister and I have the option of staying at my bfs house for indefinitely with not having to pay rent.)

So. I have an un-used plane ticket that I need to change the date so I don't lose the money on it. Should I book it for Jan 2nd and do what I want, or still try to please my mom? PLEASE...PLEASE I could use the advice, no trolls, and I need some advice right now cuz this is a lot to deal with!!

Oh, btw, I'm 21 years old, I pay my mother rent and everything every month, i have a steady job and im a full time student! I've never done anything bad or against my mom (such as do drugs or sneak out)....

Thanks