In reply to grumpybearpantsclimbinggoat:
Can you take her to a climbing shop that has a decent system for letting you test harnesses and get her to put a normal harness on and turn upside down in it to get a feel for how secure it is? It might help her get over her fear if she can actually turn upside down in one close to the ground (especially in a non-climbing environment where there's no pressure to climb in it). It's relatively easy to swing yourself upside down and hook your feet around the rope to keep yourself there. I'd imagine a decent shop would be happy to help.
Cat