Edit: Sie schreiben should be accepted (but isn't a translation of "she writes"). It's a bug, see Zach's screenshots, and report it until it gets fixed. Also, lesson learned, don't go by what is shown in the thread. Screenshots first, delete later. Ignore the rest of my post.
I just deleted a lot of posts that were erroneous, including one that had 30+ upvotes. "Sie schreiben" is not correct.
Sie schreibt. = she writes
Sie schreiben. = you (formal, singular/plural) write
Sie schreiben. = they write
My apologies for deleting most of the comments, but it is quicker and easier this way, and will avoid any further confusion. Thanks Kai for pointing it out.
You got the wrong idea about what happened though. A lot of people, including myself a few hours ago, were presented with a question which asked us to pick the correct sentence(s) out of 3 options, including "Sie schreibt" and "Sie schreiben". When clicking on "Sie schreiben" it tells you that only "Sie schreibt" is a correct option. Said form of the question says nothing about translating "She is writing" only that you should select the correct form to complete the sentence. So that is what people, including myself, meant by "Sie schreiben is also correct".
It's a pretty old error that, for some reason, Duolingo has failed to fix, despite what I am sure were and continue to be numerous reports. Actually, I just sent one in myself when I last had this question a few hours ago.
Zach is exactly correct. This problem also exists with "Sie schwimmen/schwimmt", except there the correct choice from the drop down menu is schwimmen >.<
I already submit an error report for that, but this is a heads up if you come across that problem in your travels--it wants the opposite answer as here!
Can you find it again and post a screenshot or recreate it in a comment? If it's a bug, it definitely needs to be fixed.
We may have been wrong about what happened, but seeing as this is discussing the sentence "She is writing.", posting "Sie schreiben is correct" is still misleading.
I agree with kaiengle that simply posting "Schreiben is also correct' is misleading. I personally didn't post the top comment that said that, but I did upvote it. So I think it's probably best to not have a comment like that at the top. Although, until Duolingo fixes this, it will probably happen again.
Now, after mashing the "practice" button for the word "schreiben" in my Vocabulary section, I finally got this sentence again. I really wish we could practice a specific sentence again. Anyway, here are some screenshots showing off the error.
"Stop the clutter!" - R U shouting here?
I almost always choose the shorter form (less typing): "she write" (yes, sometimes without -s) And here is a program error. It says I'm wrong. But it is not wrong it is just sloppy typing. And why is it a good answer? "she", "write", present time (!future, !past), !conditional, !passive, !reported speech, !causation or other. Subject: she; verb: write. I'm learing german (meaning not english) This kind of "error" is a typo max.