I think it's partly cultural and partly just people.
The majority of people who have come and gone in my life (Taiwanese and otherwise) had absolutely no money sense whatsoever. They would just piss it away without taking account of where it's going and where they expect it to come from, and then complain about how "they don't have enough money". However, Taiwanese women do seem to be noticeably worse in this respect. My ex-wife (Taiwanese) has an attitude very similar to your gf: basically, the bf/husband is an ATM in which you never need to deposit anything. As Deuce notes, it's very common for husbands to simply hand over all their salary to the wife so she can chuck it down the toilet, which is wrong on many different levels. Taiwanese education also doesn't offer any home economics tuition; for example, my ex didn't understand that a monthly 1.5% interest rate on a loan is larger than the 18%APR credit-card bills she was using it to pay off.
You need to get this sorted
before you have a marriage certificate, because at that point you will be in deep brown stuff, especially since your gf seems unable to discuss it like an adult (you use the word "accuse").
In my case, the ex had serious emotional issues which she soothed by running up credit card bills. Make sure your gf is not one of these. It was my job to pay all the household bills (all of them) while she spent every penny of her (not-bad) salary filling our house with useless shit that we didn't need.
So, stick to your guns over the financial planning. There is
NO other way to do it. Sounds like you've got a perfectly sensible approach (calculating recurring expenses and split between you in proportion to salaries). It is eminently fair. However, when you have this kind of non-logic to contend with:
I am a Taiwanese. and I agree with your girlfriend. I don't think anything can be actually fair in the world, especially when your loved ones involved.
it's a bit of an uphill struggle.
You might want to reframe your approach: tell her that you're planning for your future together, and trying to make sure you have a nice place to live, a college fund for the kids, and so on. This didn't work for me (I just got a temper tantrum and an insistence that she wanted all that stuff
and the spending sprees). However, it's worth a try. If it's still no-go, move on and find someone else. Financial mismanagement causes terrible stress and misery and is one of the leading causes of divorce.