You have to think of yourself first. If the working conditions where you are are that bad, and you know they're not going to change, then you need to get out of there one way or the other. Just try to remember that this is business not personal, so I really wouldn't worry about "stabbing her in the back."
My opinion on what will set your salon apart from the others with so much compitition around you, is to literally set yourself apart. Pick your location at least 20 miles away from the most busiest salons. This may mean starting over with clientel, but if the location is right, I don't believe that to be an issue.
Also remember that you will most likely break even the first 2 years or so, so hang in there if you can. This is probably going to be a risk, but the only way to succeed is to just do it. Think about, and decide if you're ready to take the risk. Of course you can always work for someone else until the time is really right.
Either way, put this salon behind you. You don't need to be caught up in her personal drama. Wish her the best, pray for her, and then just move on. Good luck!
Amy