I think your Vivian is much more like her character than the few canon age fics I've seen. This could easily be a canon episode. And I mean that in the best of ways.

Since she never returned I been sort of hoping a suitor managed to sweep her off her feet and she'd be spared a life of bitchy and longing solitude. And now I suddenly wonder if she is - since BBC does morph the legends as they please - the lady of Shalot. And that is rather tragic. No, she's a crazy lovesick ninja. No doubt about it! *nods*