How do i stop my dog from being so aggressive after second heat?

After the first heat she had, she had been a bit aggressive towards this one dog. She was being greedy about things she had, she didn't even let this one dog go near us. But it seldom happened. Then after second heat, she was wary of every dog she didn't know. we try to go to a dog park daily and it was right after the second heat. She was shockingly aggressive. But even with some of the young dogs around her age that she knew she was unbelievably aggressive with. She growled, snarled, and was becoming very dominant. I know she's finally realizing her dominance but I still want to keep her in control. I have to be much more strict now and I have an idea of what I should do but can I stop her from completely being aggressive? She's gotten better since we went there a couple of times. I'm being more dominant in the house and out in the backyard. But is there anything else I could do?