There's an old say about "roots and wings" regarding parenting: "A parent's job is to give their children roots to grow with and wings to fly away with." Your mother and grandparents seem to want those roots of yours to stay firmly planted in their own little garden and their brow-beating is their way of clipping your wings.
You didn't specify your gender in this letter, but it matters. With South American culture, it matters so much! It matters enough that I searched out your email username and found your twitter and Google+ to confirm that you are indeed female. This is the first time I've ever sought out additional information on someone who's written to me, but I needed to confirm what I suspected. Suspected? Yes indeed! Based on the way you're being treated and what I know of South American culture, it's unlikely that this was a dude writing me. Women are considered weak delicate little flowers who can't possibly survive on their own (or shouldn't, anyway). You have to stay right there with the family until a big strong man comes along to look after your pretty little head, cuz girls are too stupid and silly to take care of themselves. That about right? If you were a guy, it's very unlikely that your mother would question your desire to move out. It's pretty much like America in the 1950s and before. Retarded, ass-backward "tradition." Am I wrong here? If you were a man, would this still be an issue? Hahaha... I'm not wrong. But on the off chance that you are a dude, then I'll just say that you need to man the fuck up and tell mommy to let go of your balls. But, again, I'm not wrong.
This adds the element of ass-backward South American sexism disguised as "tradition" but otherwise it doesn't really change the advice I would give.
Independance is learned (and earned) by being independant! You are now a grown woman and there is nothing your mother or grandparents can do to prevent you from moving out. Well, there is one thing and they're already doing it and it's working. Emotional blackmail. They emotionally blackmailed you out of the college you wanted. They're emotionally blackmailing you into staying just where they want you. And that shit only works if you let it!
Despite all that, I'd like to ask what's the rush? You're 19 years old and in college. Right now, I'd advise you to concentrate on school. This is the same advice I'd give to anyone else in your situation. Stay with the parents until you're out of college and have a job. But at the same time, you need to put your foot down. If you decide to take my advice and plan on leaving home as soon as you're done with school and have a decent income, then that's what you should tell them.
And when I say tell them, I mean INFORM them, not ask for their permission or approval, because you don't need it. Tell them once, and only once. After that, you don't mention it again until the words that come out of your mouth are "I have an apartment now, I've moved most of my stuff over there, I'll be leaving tomorrow evening."
Be prepared for them to actively attempt to stop you from leaving. If they do that, you don't want a huge fight, so don't fight them. You told them this was coming. You told them how it was going to be. Their refusal to accept it does not change anything. They can't keep you locked up in the house by force when you, at the very least, have to go to work. So if that's the only place they let you go, then you go to work and then go to YOUR home afterward.
Really, you need to seriously grab hold of the concept I'm offering you here. They can't actually STOP you. All they're doing is making you feel like shit so that you stop yourself! You inform them of how it's going to be and then just don't argue with them anymore. Right now, it's an argument between you. You need to make it not an argument, but a fact of life that they can either accept or hate, but it's going to happen either way, with or without their approval or permission.
I do strongly advise waiting until you're finished with college, but that's entirely up to you. If you feel you're ready and want to leave this weekend, do it. It'd be stupid, but it's YOUR life and therefore YOUR stupid mistake to make. It isn't up to me or your mother to tell you what to do. It's up to me to advise you and, frankly, once you're college-aged, that's all your mother has any right to do either. Do what you feel is right for you and anyone else's opinion is insignificant.
In closing, I do feel I should offer you an apology. People write to me looking for advice and they expect anonymity in that process. I do apologize for looking up your twitter and G+, but I did feel it neccesary to give the best advice possible. Rest assured, I won't remember your name, I don't keep the emails I get, and no one else will ever know who you are either. Anonymity is still alive and well here! Good luck to you.
All My Hate,