Fairness is subjective. She currently has none of the legal or financial risk. None. Talk it through and just make you're not actually losing money. It's also about perception. If someone pays part of the mortgage and utilities may easily think they're a contributor, but what about property taxes, insurance, the risk attached to it all, etc???

They don't penalize you for spending a lot. They penalize for carrying debt for a long period of time. For example, if you purchase and pay off, then no impact on your credit score, but if you purchase and keep that debt, then it'll impact your credit score until you pay it off.

Why?