As a NES, this sounds odd to me. I would say "she usually recovers fast" or "she used to recover fast [but not any more]." I think the usually implies some sort of continuum that uses the present tense. Are either of these close to what this means?
Why is it "hurtigt" rather than "hurtig"? What is 'hurtigt' agreeing with here?
@rainbow: I thought so, too. But I wrote, "She usually comes quickly," (thinking of a doctor, midwife, or veterinarian), but it was marked wrong. They wanted "She recovers quickly." I was shocked... Without giving a context, how are we supposed to know she's even been ill?
Fast is an adjective which van only be used to describe a noun. To describe a verb the adverb should be used. Even so as a native English speaker I would still not say ''recovered fastly' but ' recovered quickly' .