Spaying will make no difference. What DOES make a difference is the initial training of a puppy at 8 weeks, or in a breeder's case even earlier while the pups are still in the nest. If pups are taught the recall whistle as soon as they are weaned it usually stays with them - they don't get fed if they don't come running to the whistle. The stop whistle is a life saver and instant recall in any breed is imperative. You could still do it at her age but you'd have to keep her on a line till she was doing it 100 %. NO free running
at all till you are 100% sure she will obey your commands.
Start using a whistle (carries further than the voice and in theory at least it is unemotional, although I would argue the point on that
)
For the emergency stop, have her on a lead and tell her to sit, at the same time blow a single blast on the whistle, and gradually lengthen the distance between you as she anticipates sitting when you blow the whistle, till she sits the second you blow the whistle no matter where she is - in the house, in the garden, or wherever.
For the recall put her on a sit stay, again on a short lead to start with, then lengthen it as she progresses, Walk a step away to start with and call her and immediately afterwards blow three pips on the whistle. If she doesn't come immediately give her a tug, and when she gets to you give her a very high value treat - chicken, cat biscuits, liver, whatever turns her on.
Again gradually lengthen the distance you are recalling her from. Slowly slowly catchee monkey ................ You'll go through a lot of chicken etc, but it IS worth it!
Hope that helps.
And lastly - she isn't a terrier - she is a dog - all dogs will run off and do what they want to do if they are not trained. Well,
almost all dogs. Some breeds don't bother.