[MRM]

All the business emails belong to the business. You can read them off the C drive if you bring them to a forensic expert. You can (and probably should) immediately get a restraining order against her to prevent her from using the company data she clearly kept and to keep her from contacting company customers. I'd do it right now, before the end of the week. You know she's home calling each one of her old customers and every other contact she ever heard of in your company.

However, you cannot withhold that last paycheck, even if she's stolen from you and owes you money. You have to give her the paycheck timely and sue her for damages later.