Reaching out to an old friend?

So when my fiancé and I first started dating I lost my only friend. Ill admit now that I was an asshole and definitely put her on a shelf because it was high school and he was this new guy in my life. We're all 21 now and doing that to her has been the biggest regret of my life so far. We had such a great friendship and it doesn't sit right with me how it ended. Since her I haven't been able to connect with anyone else because I feel like im trying to find someone exactly like her. My fiancé is constantly encouraging me to reach out to her and I've always just made excuses about why I shouldnt. 2 weeks ago her mom came into my job and told me I should go over and visit since its been so long and seeing her mom made me realize I got to get over myself. I wrote her a letter explaining how I felt and apologized for putting her on a shelf. Im planning on dropping the letter off at her house today but I feel kinda lame. Is this a good idea? I feel like im begging for a friendship to be rekindled when I can't force her to forgive me. My biggest fear is rejection.