I can't advise on what you're after, sorry - but would it be possible to set up some kind of CCTV system on the fence, so you can work out where she's getting out??
I truly understand your pain, as we had a similar problem with our cross Lancashire Heeler.
She dug a hole under the fence, so I ended up having to put breeze blocks in front of the fence ..... yet she still managed to get out.
One day I was in the neighbour's garden, talking to her about my dog and how she managed to keep escaping, when my dog appeared at the other side of the fence in my garden. The fence comprised of wooden posts and slats of wood with very narrow gaps .... yet the dog managed to squeeze through, right in front of us - I swear the gap was no bigger than the size of her head. Well, that escape path was blocked as me and the neighbour ended up sharing the cost towards a new fence (it needed replacing anyway and this was as good an excuse as any).
.... and yet again she managed to escape - she knocked one of the bottom panels off near the gate - so extra long screws required to fix the panels back .... and eventually we had a secure garden.
Anyway, sorry for waffling, but I think persistence is the key - you need to scrutinise every inch of your fence - you'll be surprised how small the gaps are they can fit through - if I hadn't seen it with my own eyes, I'd never have believed she could have fit through such a small gap.