well one thing for sure. report to gov or police.

Be there for her when she needs you;
How is she like when you're with her? Does she seem happier?
If it is that, I think its a good sign that you should spend more time with her; as you will be helping her overcoming her depression by helping her to refocus on the positive side of things;
Seems like she has low self-confidence and esteem, which stem from her family upbringing; hence I suggest helping her refocus elsewhere until she could solve her problem herself;

Do bear in mind that she is looking for a friend; nothing more; and only she could solve her own problems; what you could do as a friend is to spend time with her, take her out and make sure she has a good time, this will help boost her confidence and change her perception to look at life more positively;

This happened to a close friend of mine, it helped out for me as I do see improvements in that friend of mine.

Gosh, it's really sad to hear that...

In my opinion 1st thing she has to do is: Seek help from professional.

Psychology Centres usually have experience dealing with this kind of issue.
Throughout the consultations, they will advise the best way possible to your friend.

From there, I imagine there will be 3 ways to deal with this issue:
1) Reinforce her mental strength so she can endure the abuse without breaking down her mind (yes some people have mental breakdown when in great distress / feel too hopeless)

2) Leave the family. I believe your friend is already an adult, she definitely has the capability to survive by her own. Get a job, or seek help from shelters temporarily.

3) Get some footage of the abuses. Report to police, let the authority handle her parents. They deserve some jail time.

Hope my suggestions above can give you some idea on how to help your friend, poor thing... By the way please be extra cautious if you sense a hint of suicidal thought from your friend.

Be a good listener and available for her if your routine permits. Besides that I don't think there is much you are able to do since this is a domestic and family affair. Your support is already golden.

Just wondering where do your friend stays? She can look for any established psychology centre.
I do know one psychology centre situated at Puchong where my gf intern there before, you can PM me if you need detailed info about that centre.

I suggest you to check with http://www.wao.org.my/ , an NGO named asa Pertubuhan Pertolongan Wanita. They might be able to guide you on seeking shelter for your friend.

It is lucky your friend managed to find you to cling on. You have saved your friend's live.
Then there is a greater need for her to seek help from psychology centre - at the very least they can help to minimize the suicidal thoughts.

This one really, really complicated....
I personally don't see how any treatment can work in this case, not when she still has to go back to the monsters den at the end of the day. Unless of course she's sedated until like zombie.

Can use law only I guess, legally separate her from her toxic parents. Anyone got legal experience here?