I grew up in Spain; when I left, at age 18, my Spanish was on par with my native German. These days, I still understand every last bit, dialects included (I started a movie the other day and only registered that it was in Spanish when Mr Arctic came in and asked me to at least turn on subtitles ). But after over three decades of using it only sporadically, my active speaking vocabulary has clearly suffered, and I developed a slight accent as well. If you don't keep a language alive, it can get rusty after some time.I thought her french is average - she replaced some words with english and clearly sometimes was trying to recall how to say it. Strange, after all this years in France being a bit rusty - no recent practice presumably? No old friends from there left? Or her brain just doesnt function properly?
That said, she has a tough time finding friends to speak English to, let alone French ...