You need to build things up gradually with a stay. Tell Chance to stay, take 1 step away and then go straight back, if she stayed treat and praise, then take 2 steps, straight back, 3 steps etc. Once she is staying while you go straight back to him next try staying away for 5 seconds, 10 seconds and build it up gradually.

If she gets up go straight back to her and put her back in the position you left her in. If you have to constantly keep saying stay to her to start off with then so be it.

Once you have done that aim for getting her to stay for a minute while you are about 5 paces away from him, then build up like that. When you manage 2 minutes try doing part of the stay out of sight for say 60 seconds in sight, 30 seconds out of sight and the last 30 seconds back in sight.

Always praise and treat when she does as you want.

Good luck, and be paitient, it doesn't happen over night