Katymac, I struggle with this kind of thing myself. I hate delegating (110% perfectionist moi!) and I hate talking to people, and I hate asking them to do stuff, I also hate checking it and making sure they do it!
You really need to put the personal friendships away the minute you step into work. YOU are paying her a salary, SHE is working for YOU, therefore she owes you a decent day's work for her decent day's salary- employment obligations are a 2-way thing.
At the end of the day, she is taking advantage of your good nature, and the relationship you have, to claim a salary without doing all of the work- if she wasn't a friend, you would probably thinking right now 'hang on a minute? that's theft!'
You need to nip it in the bud now! The situation is going to deteriorate, and she will cease to be your friend. I really think that if you are going to remain friends, she cannot work for you, sorry, but friends cannot have financial obligations to each other. That's not friendship. If you think she is truly right for the job, then keep her, but end the personal relationship.
I know this is harsh, but I think from your posts, you already know this is the way its going to go. From what I've read your business sounds wonderful, and I really hope its a very successful one, but in order for that to happen everyone involved needs to put in their fair share of the work.
Be honest with her- tell her how you see the situation. It may be she genuinely feels there is not enough time to complete those tasks, in which case she should be having some input into the time allowed etc. If she is a real friend, she will admit things have to change too. GL {hugs}