Forgot to email a professor back about a research opportunity. What to expect? First off, I messed up big time here. I'm applying for a Fulbright academic fellowship after having finished my undergrad last year.

This spring, I figured I would email some potential advisors and get a head start on my application. I found one that was a good match with my previous work, and she agreed that she could host me as long as I got the scholarship in the end. (edit to be clear: the start date was clearly stated in our initial correspondence, contingent on me getting the scholarship) 

But this coincided with a move to Europe (I was there for 6 months on a research scholarship) - I know this is no excuse, but just to explain the circumstances better - and I forgot to reply to her.

I sent her an email now apologizing profusely, expressing my understanding that she might not want to host me any longer, and explaining the circumstances to her (i.e. if she was still willing to discuss this further). I wanted to let her know that I wasn't shopping around for other opportunities, and am only emailing her back after so long because I couldn't find anything; on the contrary, our research interests align well (it's not a huge country and this is just about the only research group that works in my field anyway).

I'm operating under the assumption that she's going to say no, but lesson learned for next time. I'm just wondering how big of an offense I committed here?
I have a friend who did something similar. She didn't realize she had a job offer on her voice mail for several months. In this case, the job opening still existed and she still qualified, so they hired her anyways. I don't think there's any reason why this has to be any different.

On the other hand, she could quite possibly have moved on to other things or hosted someone else in your absence, in which case it might just be unfeasible for her to pick you up after all this time.

And there are many people who would refuse you just on the principal that you made a mistake. I've certainly met plenty of them.

At the end of the day, you've probably done all you can to rectify the situation. If she denies you, just move on with life. If she doesn't, buy her some cookies and be happy. :)