The first bit of advice I'll give you is advice that I give quite a bit when dogs do not respond to their owners. You need to establish yourself as the alpha leader in your relationship with your dog so it will respect you and your commands to come to you off leash for example.
Here's a helpful link on becoming the alpha pack leader;
Establishing Yourself as Pack Leader
Being The Alpha Dog - Dogs & Dog Training
While and after establishing this state, you need to make it clear that your dog must come when you say so. Start simple. Start on leah. Have her sit and stay then call her name. When she comes, reward her with a yummy treat, toy, praise, or all of the above. Whatever flaots her boat

By the way, if you ever say her name in a negative tone she may associate it with something negative so whenever calling her make it all positive no matter how frustrated you may get. Positive reinforcement is the key in this situation. Outside, a much better method may be a whistle (specifically for dogs or just a standard whistle is fine) or maybe even a clicker, however a whistle is probably beter outside because the sound travels further. Take it one step at a time. As I said earlier, start on leash, have her sit, them maybe blow the whistle and gentle pull her toward you so she comes then reward her. Eventually have the leash tension allow her to go further and further doing this exercise until she can do it off lead. Maybe use an extendable leash or long rope. I sazw this method used on It's Me Or The Dog with Victoria Stilwell. It was with a labrador who didn't come so they used the whistle and yummy pieces of chicken as a reward. It worked wonders! Good Luck!
Although if done correctly and diligantly this method should be very successful, my trainer from puppy school a few years ago said that they used a long elastic rope on their dogs in the house at all time whil,e teaching them to come on command (recall). They would gentle pull on it to have the dog come. Sounds a little extreme to me but I guess it's something to try if all else fails.
Again, Good Luck!