Three legged female German shepherd - $50 (Salemburg)

I have a beautiful three legged pure bred German shepherd female.
I got her 12/17/2017 at 5 weeks old.
She was the runt of the litter.
Very beautiful and loyal dog.
I am rehoming her because I can't seem to keep her contained.
When I take her out she finds a way to escape my fenced yard.
I am afraid she will get shot again by my neighbor or ran over.
I have over 5k invested in vet bills from her that I am still paying.
I want her to go to someone that has a large piece of land that can train her to stay in the yard.
Where no neighbors will try to kill her.
I have livestock and if monitored she doesn't attack them at all.
She has gone inu goats pen only to dig her way out to go to the neighbors yard.
I am worried she will be killed.
I am willing to negotiate on the rehoming fee.
I don't want to take her to the shelter.
She will just be put down.