That’s why you don’t use Venmo, PayPal, Square etc for large transactions.

Fire her yesterday and be done with it.

Judging from the lack of info in your post you don’t have the foresight and planning to start a business. But that’s the only impression your post gives off so I have no helpful advice.

If you’re not toeing the line of burnout and wanting to quit I don’t think you’re working hard enough at least in the beginning. At some point you need to start delegating and taking time for yourself to keep from feeling burnout long term. You can only take so much, and you need to find your limits. Mental resilience is a skill to practice.