Sounds like you are getting a "baptism by fire" into the role of manager. It also sounds like you are doing quite well.
Don't freak about the additional responsibilities that the GM is putting on you. For one thing, if she is with the bank, she may not really know the business you are in. Also, she most likely has duties of which you are not even aware yet.
If you can, jot some of the duties down. Make a Word file and when you're online, note some of them. They look great on a resume if you decide to move on or get a different offer.