Is it OK to nudge an editor when you haven't had a response in a reasonable amount of time? You might get different answers to that question depending on whether it is directed to an editor or a writer. As a writer, I think it's alright to do so sometimes. I wouldn't recommend making a habit of it or the editor just might cut your name out of her list of writers. Try to look at it from their side of the fence. If 9 out of 10 writers make inquiries, it could be rather aggravating, or if one writer does it habitually, same reaction.
I had occasion to do this yesterday. I'd sent an article to an editor of a writer's newsletter. She's purchased several of my articles dealing with the craft of writing, and she's always been one to respond quickly--unlike many editors. When I hadn't heard from her in a couple of weeks, I got to wondering if I'd sent the submission to the proper address. She has several addresses and I thought maybe she only checked certain ones for the submissions. So, I wrote her a very brief note explaining that I only wanted to know if she had received the submission I'd sent due to the address issue.
I heard from her in minutes. She had not received it, and then she qualified that by saying that perhaps she had gotten it and it was on the bottom of a pile she'd yet to attack. "Please send it again," she finished.
I immediately copied and pasted it into the e-mail and clicked Send. Within twenty minutes, I had an answer. She liked it. She wanted to use it. Would it be alright with me if it was not published until the August issue?
In this case, if I had not sent that little note of inquiry, my submission may have been lost forever. So, do nudge on occasion. Don't do it frequently, don't do it in anger or frustration, don't do it because of your own impatience. Have a valid reason. Some editors respond fairly fast while others take what feels like forever. As you work with them, you begin to know how each one works.