Since the mishap (as I'll put it), I got Ryuuko a medical bracelet. It wasn't the prettiest looking thing there was but it was necessary, regardless, if Ryuuko was annoyed with it (which she was, for obvious reasons). The fence took a bit longer and Ryuuko watched with anticipation as the fence was being put up. The noises would cause her go to the back of the house but she'd promptly return to observe the actions present.
I oversaw this and, frankly, I doubt Ryuuko would be capable of climbing over it and neither did she know gates worked, thus I needn't worry too much about her trying to escape. Of course, she'd probably wonder if she should try clawing under it before coming to the conclusion to just stare at the damn thing. Once it was finished, I thought I'd let her outside to grow used this safety measure.
Once outside, she sat for a while before coming towards the fence, shaking it, coming to the realization that it wasn't much different from what was in the backyard. She doesn't usually draw on past recollections but she did, it seems, connect the noise with my explanation of a fence being there for her safety.
When her flashback ended, she decided that the fence was an amusing sort of the device, considering her shaking caused it to make noise and she decided she didn't mind the noise.