I agree, your very first step should be to thoroughly research your local ordinances regarding chickens to make sure they are legal, especially if you anticipate any problems from the neighbor. If you're legal, then you don't need to convince your neighbor about anything, as long as you stick to the letter of the law all she could do would be to complain. I did warn my one neighbor that I anticipated problems from that we were planning on getting chickens. I also told him we were planning on getting 15 and having a rooster, so when we ended up getting only 7 it wasn't as bad as he was expecting. He still complained that the chickens were causing mice in his garage last winter, although after setting traps and following up with him he quite sheepishly admitted that he hadn't had any more problems with the mice since talking to me. But he's just one of those guys that would find something to complain about no matter what.
Chickens, even hens, can be loud at times. My neighbor on the corner, the one that has a house between mine and hers, can hear my chickens. She just recently moved from a larger city and at first thought they were geese, but she does seem to appreciate the ambiance. Yes, the girls are loud, but they are not constant. And they generally aren't any more bothersome than any of the barking dogs in the neighborhood. I did get a rooster in October, and so far I haven't heard any feedback from the neighbors on him and his crowing. He sleeps in the garage at night, so that his early morning crowing is less bothersome to the neighbors, but if *I* can still hear him in our bedroom (albeit muffled, he has yet to wake me from the garage but I can certainly hear him if I am already awake) I'm sure the neighbors can probably hear him too. In my town, roosters are allowed so long as they don't violate current noise ordinances. I've known people who have successfully kept roosters, and I've also known people who have had to get rid of their roosters because the neighbors complained. So we're waiting to see how it goes, if the neighbors complain about him he will be out of here.
Smell and flies will definitely be kept down if you stick to a regular cleaning schedule. And you can scoop chicken poop like you do dog poop, in the warmer months when I'm really good about getting out and picking up the dog poop daily I actually pick the chicken poop up too right along side it. Dog poop goes in the trash, chicken poop goes in a separate bucket that gets thrown on the compost pile. But like others have said, keeping things dry is the real key. No matter what, there is an undeniable funk to my run in the spring when it's just so wet and there's nothing I can do about it. Fortunately, that funk doesn't seem to travel very far and I have yet to hear any of the neighbors complain about the smell. I can smell it from a few feet away, but not from across the yard.