Problem bonding with horse?!?

I have just started leasing a new horse, Spirit. She is a 13 yr old half arab. Her first owner was a real bad guy. He would whip her with a chain lead rope when she misbehaved. She was then bred and gave birth to a stillborn foal. Her second owner had her fully trained well and took good care of her, although he never saw her alot. He boarded her at my best friend's stables where I met her. Now, I am leasing her. She was at first very, very jumpy and hated leaving her herd. I worked with her A LOT and now I am riding her with my friend. She still jumps at tiny things. The first few times I rode her, she was great. Now, she hates being ridden and trys to do anything to get back to her herd. I feel like I have given her all of my affection and time and in return I get a horse who wants to run me over to get back to her pasture mate. I know she was abused and horses are herd animals, but honestly I do not know what to do anymore. I have always wanted a horse and everyone knows a girls dream horse is the perfect best friend. I do not want to give up on her yet, so how do I get her to trust me? Any methods or exercises? I groom her to perfection, feed her her favorite treats, scratch her favorite places, read to her...do everything! I see my friend's horse go to her, nuzzle her and their bond is evident. For example the other day, my family went to give her a carrot and visit and her pasture mate came running over. I stood waiting to give her a carrot and a good scratch and she blew right by me, didnt even glance at me. So how do I get her to trust me? How do I get her to stop being so herd bound as well? I know abused horses need special attention, but how? And please no answers saying she is too much horse for me...I need lessons...etc. I am feeling like I am giving up on her, and the lease is up in december. After that, I can buy her...but at this point....I dunno.