I KNOW IT SEEMS LONG, BUT PLEASE READ IT AND GIVE ADVICE.
So, my sister is getting married next week and is going to live abroad from then on. My mother is very upset, for several reasons.
1. My sister hurried up her wedding because her fiancé was offered a really good job abroad. She barely gave us time to come to terms with her definitive departure. The whole thing takes place in just a few weeks. And she wasn’t even telling us upfront, we basically had to ask her what was going on. I was supposed to be her best friend, by the way.
2. My parents paid for my sister’s master degree and she said repeatedly that she was going to star a business with my mother once she’d finished her studies, as a way to repay them. She lived at home throughout that time and quite her job, even though it was a partial time masters. She had an eye surgery two years ago, but it’s been over a year and a half that the doctor said she was ready to work.
3. It’s been barely a month after she graduated and instead of announcing the start of the business with my mother, she announced she was leaving the country not to come back. Even though, in the past, she had said she wouldn’t live over two years on a different country. This was the first time in her life she said she was moving to a different country, for good. This was two weeks ago, and she is getting married next week.
4. No, my sister is not pregnant.
5. My mother also is very close to my sisters and me. The truth is that the marriage with my father plainly sucks. He’s not a terrible father, he has provided for us for a long time, but he is a terrible husband. He recently confessed cheating on her for years and sometimes gets drunk. So, my mother, I guess being a Catholic, had repressed her own happiness via divorce for years (now she's "considering" it). Thus, developed a really strong affection for her daughters. She is a wonderful mom and has always been there for us. But, in an unconscious way, emotionally blackmails us not to leave her.
6. Now, summing up the attitude of my sister, my father's character and my mother’s predisposition to hold on to us –her daughters-, you can imagine what is going on. My mom feels resentful, betrayed and sad. I, too, felt resentful to my sister -best friend- for doing things so hasty, but I have decided to let go.
It’s probably not my job, but I want to help my mom, or at least, get her the help she needs to: free herself from her daughters, forgive my sister (for her own peace of mind) and find her own happiness. My mom is also hypertense, she doesn't take bad news the right way. How can I approach her? What should I say? How? Books?
I'm almost 24 and I want to study abroad. I have said it before, for years -unlike my sister-, but now it just feels bad timing to even mention it. I feel guilty for wanting to leave my home and, on the other hand, for not living my own life. I'm stuck, so stuck that I don’t even know what I want to do anymore. I majored on accounting and I don't like it. So any advice for me would be great too.
PLEASE HELP
So I can totally understand why finding out your sister was going abroad indefinitely would rock her world. A shock like that, in my very humble opinon, will simply take some time to lessen. No matter her initial reaction, I think she'll just need time to deal. 
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