Practical use of crypto

I have a practical real world use question about crypto.

My wife and I have separate banking accounts and we split EVERYTHING. We are constantly sending cash back and forth to each other. Every month she writes me a check for her portion of the mortgage. I deposit that check and then wait three to five business days for it to clear. Then I can finally pay the mortgage. I’m looking at using crypto as a new way to transact with her. My concern is that we will end up paying taxes on our exchanges. We are married and we file jointly. As far as I’m concerned, us exchanging currency is the same as moving between two of my own personal accounts and shouldn’t be taxed. I was considering having her buy USDC from Coinbase and sending it to me offchain to avoid fees. Then converting that to USD to pay my mortgage. Does anyone else have any idea how we could efficiently transact between each other without having tons of fees or extra taxes?