Great suggestions
I wonder about using a strand or two of wire
behind the net, so that she gets zapped as she struggles through, but doesn't know that it's not the mesh zapping her

. Might work!
And test the shock yourself. Use a blade of grass (a flat, wide blade, like you would use to make a whistle noise) to reduce the belt that you get; if you have to hold the grass within an inch of the wire to feel a pulse, it's nothing like enough of a shock to deter an determined sheep!
And having said both of those things, I felt I should also say - make sure the mesh is delivering an appreciable bolt
before doing the 'wire behind' trick. Otherwise, if you do both together, she could get into quite a pickle as she tries to retreat from the wire but is getting significant bolts from the mesh
