I had an interesting experience yesterday flying back from a quick visit to San Francisco... A Chinese woman was seating in the aisle seat, next to another woman, and I was in the window seat, so I could easily hear the conversation beetween the two women.
The Chinese woman struck up a conversation and quickly moved on to a question: "Is it incorrect to say 'speak wrongly' in English, for example: 'People in America don't correct you when you speak wrongly' ?"
It turns out the Chinese woman was in San Francisco for an English class and had chatted to someone earlier that evening while waiting for the plane. She had lamented the fact that people generally don't correct non-native English speakers when they make mistakes. People are too polite or forgiving and let things slide, assuming they understand the gist of what the non-native speaker is saying. The other person, thus encouraged to be critical of her mistakes, had told her "You can't say 'speak wrongly', that's not correct English. You should say 'speak wrong'..."
So, fast-forward to the conversation next to me in the plane, and the Chinese woman has just posed the question to the American woman next to me. "Yes, that's correct. Wrongly isn't a word", she said. I could tell the Chinese woman was puzzled and trying to make sense of this - she had been using wrongly for several years. (I should add that in general her English was good, with a fairly heavy Mandarin accent though).
The Chinese woman seemed to have a superior grasp of English grammar and asked the other woman "But isn't wrong an adjective? Can you use it as an adverb too? 'Speak wrong' means that wrong is an adverb, right?" The American woman seemed a bit confused at this and admitted that English was never her strongest subject in school, so the academic discussion ended there.
It should be obvious that I was squirming in my seat and wanting to butt in, but I wasn't sure how to enter the conversation and not make the woman in the middle of us feel bad, plus I would then be talking over her to the Chinese woman, possibly for much of the rest of the flight... So I stayed quiet.
Needless to say, wrongly is a word and can be replaced by "incorrectly" in the Chinese woman's original usage: "Speakign English incorrectly". I hope she does a check in her dictionary when she gets home, or asks her English teacher. Then she can confidently correct people when they tell her she's "speaking wrong" in future! :)