My dog has ADHD!!!!!?

I tried walking my dog around the yard becuase I'm trying to leash train her and it was going great until a women walking with a baby stoller ped our house. She managed to wriggle out of the collar and probably would've pounced on the poor ladys kid if My gate wasn't closed. How can I stop her from backing out of the leash? It happened 3 times times and she always runs away its such a pain.