Decline fellowship offer after writing proposal together I am PhD student in my final months, and I know that I don't want to stay in academia forever. However, I wouldn't mind doing a postdoc for two or three years, because I really like the academic work.

I have written a postdoctoral fellowship proposal together with my potential future host. The host has agreed to fund 1 year from her own funds, while the fellowship pays for another year. A few days ago, I have been awarded this fellowship. 

In the meantime, I have also applied for industry positions (as I wasn't sure whether I get the fellowship), have recently had an interview and just now I got a job offer ready to sign.

Now, I have to choose between the two, and I am inclined to take the industry position and to leave academia for good - because the company has been on my "wish list" for many years and I potentially might regret having declined the job offer in a few years.

However, I am not sure whether this is fair towards the professor, as she has invested a fair amount of time into the proposal. I have not told her anything about the fellowship outcome nor the job offer. Could I still decline the fellowship without bad feelings, or have I already committed myself into this postdoc?

somewhat related:
How to politely decline a postdoc job offer after signing the offer letter?
Please note, I have not signed anything yet, so I am asking from a moral rather than a legal perspective.
Life is too short to throw away several years of your career doing something you don’t want to do in order to protect someone from mild disappointment. It is nice of you to worry about the professor, but she is responsible for her decisions, and knew that the work she was putting into the fellowship application might not yield any return, either due to you not getting the fellowship or for other reasons. So in my opinion your moral obligation in this situation is no different from your legal obligation. By the way, the legal obligation would also be pretty minimal even if you had signed acceptance of the fellowship, considering that having a postdoc is not the same as being an indentured servant, and it is quite common for postdocs to decide on a change of career direction. 

Good luck!