Advice Needed: Split expenses equally or by percentage w/ gf?

So, my gf (24) and I (28) live together and finances is a topic of frustration for both. She values spending her money on food and clothes. I value spending money on travel and experiences. I make more money than her and she’s frustrated I do not pay more for our life together. (I.e more rent) I’m frustrated that she has these thoughts as I don’t want to subsidize her lifestyle like I’m her parents. Note: we did the math and I pay an extra $250 per month on treating her to dinners, etc so it’s not a 50/50 split.

Question: Should we be splitting rent in half or paying rent as a percentage of our income?

Thoughts?