I have been filing relevant documents per your advice. All utilities have both our names, we’re both on my car insurance policy, named as each other’s beneficiaries on everything, I’m on her health insurance policy, both on the lease, and just opened a joint checking and savings account.
As for the credit card - her being incredibly patient during the K1 limbo and my lack of an income has meant that she has not made all her full payments, as we both normally would. I may wait until she is back on track with that (with my help now I’m working!) before becoming an authorized user, plus I have my own card to use for now.