The long lead is exactly what I was going to suggests too!
What I can add to this is my three are NEVER allowed out the front door. They were trained to only use the back to always. So when someone does come to the front door they do not bolt out.
What I did with the back door training is I made them sit and stay on command until I am read to let them go out. They all sit, stay and look at me no matter what until I tell them to go. They also do not run out the gate when we go in and out. It has never been allowed.
If you have a bolter you need to keep her on a leash at all times. If she starts to take off you can alwasy step on the end to stop her. But then tell her good girl and treat and praise.
A lot of this information is also in a book that I like to recommend.
Let the Dog Decide
It really is a great book and I only paid a few dollars for it on Amazon.