EllieT, A isn't fully bilingual, but I do speak a lot of French with her (although it's getting harder now that she's stubbornly refusing it in favour of English). I've also read that bilingual children tend to talk later, have fewer words in each language and don't always sound as fluent because the total number of words is about the same but divided by the languages. It does catch up eventually.
Don’t give up on the French though. I’ve read it’s very common for bilingual kids to go through (longer or shorter) periods when they refuse one language (usually the minority language). But if you keep it up she will probably get back to it. And even if she is refusing to use it she will learn to understand it.