Establishing appropriate title for key employee

Need some help here...I'm having a hard time coming up with a proper title for an employee. She is by far one of the smartest people I have met. She wears many hats and we're not sure where we'd be without her contribution. Here's a description of her duties, efforts, and workload. This is a specialty retail environment and a new business.

She's salary and often puts in 50 hours/week. That's in the building, so not including time spent at home researching/making phone calls/answering emails/planning/writing etc. So potentially 60 hours/week. It's safe to say she works as hard if not harder than the owner. Her job includes ordering product, establishing prices, overseeing some operations, some management of other staff, product research, customer service, creating sales, this list actually could go on much longer than that. She's the highest paid person on staff, higher than the owner. She's a critical employee and considered to be an expert in the field. She could easily go somewhere else and make a significantly larger salary in a more organized work environment with less responsibility and stress.

What job title would you give someone like that? I want the job title to encompass all that she does but it's so difficult to come up with something.

Any ideas?