If a modern office-lady in Osaka slipped back thru time, how far back could she go and still make ordinary conversation?

I'm used to the idea of Japanese requiring knowing several sets of vocabulary and when which of them are appropriate. Would any of these help our time traveller? Are some areas of Japanese older than others?

Would an acquaintance with kabuki or noh help her out? Or is 'Shibaraku' weird language even for its own time?