You crave to.
I can't be her armour anymore bc that will lead to nothing but destruction in the long term (God! I'm dramatic)
So how do I help her help herself

As much as other people may make (and tell you) that it's your responsibility, it's not. She will have to learn to help herself. She may need therapy or some maybe even some chemical medication to help her move past whatever it is she needs to move past. By any chance, has she had some trauma? Something that might explain why she is the way that she is...it's perfectly ok if she's always been that way. She may come out in time or she may always stay that way. It's more important to accept her for who she is and accept that the only person who can make her change is herself.

It's sweet that you love her so much. She'll come out on her own, in time. For now, you could try and relate to her on her level. What books/shoes does she like? Are there cons or other social events relating to themse books/shows you could take her to?
When you say she doesn't fight back, what do you mean? I grew up super introverted, and if someone was being terrible to me I would mentally roll my eyes and tune them out. I'm betting she has her coping skills in place, but there so unrecognizable from yours that they don't register. You could maybe talk to her about it: tell her you feel like people push her around. Give her a couple specific/recent examples and get her to tell you how she processed them. I'll bet she's more intricate and kick-*ss than you thought.
Once she has a clear direction in life, I'll bet she will come out of her shell. That's what it took for me, at least.

Im not exactly sure if she had had gone through any traumatic incident, we weren't close until my early teenager years when I learned how to ride a bike and visited her often. So her childhood was unknown to me.
I suppose it's bc of who are that we get judged a lot.
My family is not at all a typical Asian/Vietnamese family politically, economically, my father generation for some reason let their children grow and thrive as we are. Wildly and uncontrollably.
We, me and my cousins have different way to cope with the judgements.
My other cousin forces herself into the ordinary. She becomes a teacher although she has always disliked it bc "that's how things are"
Me? I don't give a damn and if I do, it's to talk back and piss people off.
And this cousin of mine, she's terrified.
If I suggest her something that's good for her, the first thing she asks would be "will you be there too" if I say no, she'd definitely say no
It's not that I don't want to be by her side, I just

Want her to be okay by her own
What if something happens to me? Then what???
She has so much in her, she just needs to learn to show it to the world.

It sounds more like she's suffering from severe social anxiety, rather than introversion. Or perhaps a combination. Introversion has less to do with being *afraid* of people, and more to do with becoming exhausted/drained from spending too much time around them. Social anxiety is often very deeply routed in a fear of judgement/being judged

Not that I'm an expert, but unless she's willing to work with you on it to a degree, there's not a lot you can do. A lot of people with social anxiety tend to have hyper-critical thoughts about themselves. And, to make it more fun, they assume everyone else is thinking about them the same way. It's a vicious circle where they're terrified of being judged, but convinced they're being judged all the time anyway, and so try to avoid situations where they *can* be judged as much as possible.
I'm not sure if weaning her would be a worthwhile endeavour. Taking her places she's uncomfortable, and gradually leaving her by herself for longer periods of time. First time you go for maybe 5 minutes. Next outing you go for 10 or 15. It may also be practical for her to get something to fidget with. Not talking about a spinner necessarily, but a ring, or a necklace she can spin or twist to help distract herself a little when you're not around

Honestly, just talk to her if you are worried about her. There’s nothing wrong with not going out to interact with people. If it weren’t for my friends and classes, I probably wouldn’t leave my apartment. Maybe suggest she take an interesting class, like zumba or baking, so she can learn a skill while being around people but not technically having to interact with them. The key is to let her come out of her shell at her own pace.
Also, being afraid of the world is natural. I feel like I am similar to your cousin in that if something goes wrong, I won’t fight back either. I’ll sit and let it happen then stew about it later, because I hate confrontation and I’d rather not escalate the situation. If it is not life or death, I’m fine with staying silent and letting it go. This might be how your cousin deals with things.

You're probably right, she must have some sort of social anxiety.
Medical help is not an option cause in here, you only go to the hospital for the following reasons:
1. You're dying
2. You're going to give birth
3. You have a flu which basically makes you feel like you're dying
I'm seeing her later today (for another thing cause she can't go along so I ought to drag my exhausted, lack of sleep ass out of the house) I'll confront her.
This will be painful for both of us

That really sucks (<- not even remotely the right word for this, but you understand the sentiment hopefully). You'd think after how long humanity's been around we'd have come further in getting rid of stigma about things like this (or maybe it's a different issue, idk, sorry if I'm making an assumption).
I hope it goes well for you. Unfortunately dealing with social anxiety is a bit like dealing with bi-polar disorder or any other mental disorder in which it can be a fairly full-time job. That said, it can't be *your* full-time job. From the sounds of it, you have more than enough on your plate. She's lucky to have you, especially given the stigmas you both are probably up against. Hopefully it goes well for you. Maybe once she realizes how concerned you are, and what she's dealing with-- and that it's something lots of people go through-- she can start taking steps to find coping mechanisms

She could likely be introverted on top of being socially anxious, and if that's the case she will never be the type to go out and seek adventures of entertainment with unfamiliar people/situations. But hopefully for both your sakes she'll be able to find ways to function at least at a minimal level even when you're not around

Support her in any way you can