Life is funny. I have no doubt if ever I couldn't handle my poly relationship with Redpepper she would still be my most trusted best friend. My love for her would just be reshaped in a way that I could live within and be happy. There would always be a part of me in denial though..probably eternally.
Just be the best friend you can be is my advice...and make sure she knows that "friendship" is why you do the things you do for her, we mono people can be very suspicious LOL!! I get that you truly care for her and love that. I'm all about the caring!!!!