A girl waiting alone is a good chance for a girl perhaps waiting for me. ;) If you frighten her away, I'll have less chance to find the right one I am looking for :)
Sorry for the late reply :D
You have to know that the Hungarian course uses recorded audio, not computer generated voice. All samples must have been recorded with a paid contributor and in certain cases this may be the reason. If you find a sentence where the audio is missing and it would be crucial, please do report it! "Audio doesn't sound right" is a good way, but if you have an option to give detailed non-template message, that is useful, too. And though I wrote about expenses, don't let you detained to ask audio for those sentences that you need them. Contributors will decide whether they could manage it or not ;)
I thought "A lány egyedül" would be "the lonely girl". Could that be a possible answer? (In the given answer, egyedül acts as an adverb).
Edgyedül is an adverb, which you can see at the -ül suffix. (Which is by far not the only suffix for adverbs.) And, if an adjective is attached to a noun, like "the pretty girl" in English, it has to go in front of the noun as well in Hungarian "a szép lány".
Sometimes "A" is translated as "the" and sometimes as "a". Was there an error?
The Hungarian a is the definite article. That means in the vast majority of cases that it should be translated as "the" in English. The main exception is if you talk about general concepts, where English usually doesn't use articles: "Bees are yellow and black" - "A méh sárga és fekete."
My answer, "The girl is waiting on her own." was not accepted. I did report it, however, if it is not deemed correct, I will never know. To me it means exactly the same, and is an oft used English expression. But, what will Duolingo say?