You have not made a mess of things!
You have a challenging issue at the moment, but its hopefully fixable. You just sound a bit overwhelmed.
In the other thread, someone had a good idea of how to put up electric fence, but...
If you want to try a cheaper option, I'd get plastic electric fence posts, the really lightweight type, use cable ties to attach them to the existing fence, , then get a few rolls of that fluro coloured, plastic ribbon stuff that surveyors and builders use and run that instead of electric fence tape. It may be all that is needed and if she does jump through it, it should break easily and not injure her.
My hesitation on the electric fence itself is that unless she has dealt with one on the ground and knows to stay away from it, its not going to be effective. She might try to jump through it, and in that case she will not be earthed so won't get a zap, a bit like when you grab one with rubber boots on, you might get a bit of a tingle if the boots are wet, but it doesn't hurt. However if she jumps and gets tangled, that tape is quite strong and might injure her, especially if its zapping her and she panics etc etc. Worst case scenario I know, but possible if things go bad.
Just my opinion though, and I am a worrier so take that into account