Asklemmy

There are a million possibilities and no single right answer. Strangers on the internet are not going to be able to tell you. Strangers on the internet certainly don't know the dynamic between the two of you.

Write down the possibilities (you've mentioned some in your post). Think of what seems fair to you. Show her the possibilities and talk about it and agree something.

My wife came from a family that considered it the man's duty to pay for everything and that women have to protect themselves from exploitation by guarding their own money. Conversations about sharing expenses were very unwelcome and showing love meant spending a lot on luxury gifts. She used to earn a third of what i did and had more disposable income than me since bills left me with little disposable. You could end up with 2 people at different levels of affluence in the same house if you are very defensive and financially isolationist. It's taken a long time to change that to a collaboration to work through life together with shared resources.

The most "scientific" way in a full commitment would be to put an equal % of both salaries into a "bills" account, then put how much you both want to save into a savings account and then divide the leftover disposable equally between yourselves.

Or if you're too early to be fully committed then you can start with continuing to pay for everything or ask her for a flat amount contribution.

Just know that money is one of the biggest sources of friction on a relationship and most people at not on the same page. It takes work and talking to get to the same page (that means talking to her.... Not us).