Well done!
Now she has got the idea still keep it nice and slow progress so she never breaks a Stay.
Don't rush her.
A good thing to do is to start moving away in different directions, only five or six paces.
Start at the front as usual, then try moving to one side and going back (both sides, alternately) so you are eventually at right angles to her body. Next step is to be going away obliquely behind and finally walking away from the tail end. You are sort of working around the numbers of the clock, if you see what I mean.
Moving around a dog in a Stay will help to consolidate her keeping to one position and no wriggling round to see you but do work up to it.
Another thing to remember is when you get back to her, count to 5 in your head and then give her the release word/fuss/treat whatever you do. Then you can build on going back to her, not giving the release and walking away again. So you can move around, back to her and away again and she's still in the Stay. And a huge fuss when the exercise is completed of course. If you can do this by Christmas/New Year she will have done brilliantly (and so will you!).

Sgurr

Glad she's master it, sounds very promising

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I work my life around my dog, not my dog around my life