Some Background
My girlfriend's family moved to the US about 2 years ago to escape their home country (which is going through political and economic turmoil) to start over. Her mom sells insurance, and her dad works in IT.
My girlfriend (17) is the eldest of her siblings. She has a brother who we'll call Sebastian, and a sister who we'll call Valeria.
We've been dating for a year.
The Problem
I have strong reason to believe her parents have an emotionally abusive relationship with my girlfriend and her brother Sebastian, which has gotten physical at times.
Many times have I witnessed them lie blame on and guilt trip her for issues that aren't her fault, minimize her problems and make her feel sorry for trying to tell them about issues she's dealing with, deny or change promises they've made previously, and give little to no trust with no reasoning.
The result is a seriously damaged self-image, almost constant self-loathing, depression, not being able to stand up for herself, and giving up on any help fairly easily. She is constantly apologizing for herself, saying that she is a bother or that she is abusing her relationship with me.
They aren't the most responsible parents either.
Just recently, her dad and uncle could have gotten in serious trouble while driving drunk. Her uncle had fallen asleep at the wheel. Luckily, nobody was hurt and the car was fine.
What makes matters worse is that her dad on multiple occasions has driven her family while drunk. If caught (especially with her and her siblings in the car), it could ruin everything they've worked for in the past two years as they dont have their citizenship status yet and a charge like that (DUI with minors in the car) could result in deportation.
Examples of Unhealthy Behavior in the Relationship
In the past, her parents have looked at pictures of her on social media (Instagram & WhatsApp) and criticized her appearance, pointing out specific features and saying that she looks ugly or unattractive. She now has no posts on her instagram, her whatsapp pic isn't even her anymore, and she has very low confidence.
Her parents are constantly asking her for money she gets from her job, which is somewhat understandable since they send some of it to the family she has left in her home country. The issue is they get upset if she uses her money to buy things she needs or wants (clothes, food, makeup) and they also complain when she doesn't have any money left to save. They've also threatened to make her quit her job if she doesn't pay them. Her parents also seem to want 100% control over what she wears, what she does to her hair, and what she buys.
They only trust her/us when it's convenient for them. For example, if they've forgotten to pick her up or they know they'll be really late, and if I'm with her I'm allowed to drive her. Otherwise, they'll go out of their way to make sure she's never in my car.
We FaceTime pretty often and on two or more occasions her parent's have punished her saying that she was changing or was indecent in front of me (which was not true, she left me in the other room). Both occasions where based off of dramatic assumption and she was punished without need for proof. The first time it happened her mom told the rest of her family and she was so embarrassed she cried herself to sleep.
Recently she wanted to go to a concert with me. She bought tickets for both of us and I was gonna pay her back with some money from my next paycheck. Her mom told her to buy a ticket for her (since she obviously doesn't trust us) and said that she would also pay her back. Now, when my girlfriend is asking her mom to pay her back, her mom scolded her and told her she was an "ungrateful child".
Her mom has also said to her in the past "Your life does not belong to you, your life belongs to me", "You could never live without me" and other similar phrases of unhealthy dominance.
My Question
My girlfriend has realized that some of the things her parents do are not right, but she has become so used to the way they treat her that she thinks most of these things are normal in a parent/child relationship. How can I help her see that these behaviors from her parents are unhealthy and also help her defend herself from verbal attacks and manipulation from her parents?
What We've Tried
She has tried confronting her parents over problems she's dealt with and they continue to mock/mimic her or call her crazy or delusional.
I've tried to be there to listen to her and be that shoulder she can lean on when things get really rough with her parents. I remind her that what they're saying holds no actual truth and that she has never been annoying/bothersome. I am also constantly reassuring her and reminding her that she is intelligent, talented, and beautiful and that she is her own person (she would be able to live without her parents/they don't own her).*
*I've seen improvement with her self-image and confidence though the timespan of our relationship; however, quite often she'll fall back into that cycle of self-loathing and feeling helpless.
UPDATE
I have provided more information as well as an unfortunate update in this question.
--
Thank you to everyone that can help (and that has helped thus far)! I really appreciate it!!