Attacks other dogs

Hi, I'm Looking for advice on how to stop my dog attacking other dogs when out walking. I have a 7 year old female who i rescued a few years ago and i can't let her off the lead when other dogs are about as all she does is attack them. Even when on lead she growls and and becomes very aggressive. Any help or advice would be much appreciated.
Thanks.
Chris and Delphi

Have you tried walking her with an older non dog aggressive dog?

You may want to contact a professional behaviourist for some one on one training sessions.

I'm afraid I don't have any experience with aggressive behaviour, you could use distraction when walking passed other dogs but I do think kathys suggestion maybe worth while looking into   

you have to keep the dog on the lead, dont matter what you do it wont change their mind

my sam hate bigger dog so hw stays on the lead

You can find a fenced in area like a tennis court no one is playing in, playing ball and chase will be safe in there.

I used to walk late at night when no one was around, this way I could let my 2 dogs off leash and bash tennis balls as far as I could in the soccer field. I also found some cool glow in the dark balls but they got chewed up and I was afraid of the chemicals.