The Game People Play(1)

I am not sure how to categorize what I am experiencing. I have been with my current company for almost two years. The company hired me for a new position that was not even opened yet but offered me a temporary job in an entry level area to begin(if I wanted) until the new job was ready. I took the entry level job just to get my feet wet and acclimated again to the industry.
I was there for six month - got the promotion - and then started the new job.From day one, I have met with constant opposition from supervisors and coworkers.Apparently, the news of me getting the new position over the old timers was spread around.There is one particular young lady who at every opportunity has tried to get me fired and now this young lady is in my new department and my boss has given her my old work and some new work that I actually wanted to do.
I was also giving a new client and handles new business with flying colors but this young lady harbors resentments and just recently when I was at home on a Monday morning caring for my son who was sick she decided to called  on my cell to see why I was not at work(I have already left my boss a message).
This was just icing on the cake due to the fact that this is not the only time she has tried to make me look bad in our manager's eyes. I am not sure what to do and I cannot stand to be around this person due to trust issues. Do I have any legal recourse?
To make matters worse, my boss is always protecting her and depending her when she makes mistakes or is gone for two hour lunch getting nails done or takes a four day weekend without prior authorization. I have kept quiet. It just seems that I am always being pulling into her web of games because she is trying to take the heat off of herself.
I am desperate for advice.There has to be some way for me to keep my job and my sanity while having to work closely with this person.