If you have time to read the links I posted, Grendel, I'd love to know where you'd rate your daughter on that scale. Maybe 3+? Able to converse well on many topics, but with some pronounciation errors?
Beach Girl, you brought up kind of what I was thinking. I considered taking the FS exam once and looked into those requirements. What they are looking for is someone who can communicate in that country's 'standard' dialect, eg, high German, not low German, or proper Israeli Hebrew, not Yiddishe-accented Hebrew.
Most people will never, ever ever lose their accents. The accent decreases, but it's still there. Post-lingual acquisition means you'll not achieve the same level of
accent fluency as a native speaker. Someone coming to the U.S. at age 12 and speaking English as an adult may have very proper English that sounds almost like a British accent.
Obviously, working with the CIA is a bit different than being a diplomat...I mean, a diplomat has to have fluent foreign language skills whereas a CIA operative may need to pose as a native speaker.
That usually requires someone to be bilingual from childhood. I assume this is why the FS has scales that deviate slightly from traditional linguistics.
Fluency is a matter of understanding and being understood. Someone who is from Northern Minnesota and has 'bad grammar' is still fluent.