How to gain the trust of a horse?

Okay here is the deal. I have been wanting a horse for a long time. I can ride really well and I am a good horse handler. So now I have the opprotunity to lease a horse who is at my friend's stables. I know the horse a little bit, as I feed her and water her whenever I visit the stables, but I have never actually spent more than 2 minutes in her stall. I am really worried. I want to connect with her and feel a huge amount of trust, as it is with most horse owners. So how do I gain her trust and affection? I can go over to the stables as much as I want, as it is only a 5 minutes bike ride. I can not ride her yet, as she needs to be trained a little bit (YES SHE IS ALREADY TRAINED, BUT HAS NOT BEEN RIDDEN FOR A WHILE) Just a little refresher. But with groundwork and all of that until I can ride, how can I get an iron bond with her before summer when my friend and I are planning on doing all sorts of horse-oriented things??