She is critical of me because my husband and I have separate money. She says we should put our money together as a test of our relationship. She also says that our reluctance to do so means we don't trust each other. But we are very comfortable with this arrangement. She is neither right nor wrong.
Many younger spouses keep their finances separate.
Couples like you hardly give this any thought until someone brings up the issues like your older sister has. We do not think separate money means you do not trust each other. It is more likely this is just more convenient. But the issue does bring up one thought. We think it is important to have some because it does give something tangible to share equally in other than children.