I Earn Much Less Than My Partner, But We Split Costs Evenly. How Do I Stop Resenting Him?

The first woman has been with a guy 4 years, they’re not married, she’s pregnant and working part-time making $379/week take-home while he’s making $110,000…and they split everything 50/50. Why?! She’s unhappy and resentful, but she stays.

Edit: thanks for the awards!