Good luck man. We are here pulling for you. You know best on you secret, but be honest with yourself, it is a secret best told before you are on the brink of losing your mind. I am not one of the "you owe her the truth" guys, but you need to monitor it closely. I too like Worktowin wear a suit every day and dipped a can a day of cope in that suit in meetings. A hell of a ninja dumbass i was. My family knew but not my work. I had no intention of telling work until several guys here convinced me otherwise. Damn glad i did, 2nd day in my assistant walked in my office and sent me home, she knew I was starting to make an ass of myself due to her awareness of what I was going thru.
Just keep an eye on it, you may not act as stupid as me lol (I really was low on the IQ during my first week) but if you start getting agitated, anxious, or stupid you will have to tell her. Then you may find yourself dealing with her pissed and hurt while you can barely think and are as anxious as you've ever been. that would suck.
Actually fuck all that I just said. Either tell her or go on vacation and leave town, tell her your out of phone service for two weeks. Odds of you pulling this off are not high. This is going to suck. It's going to hurt. You are going to have moments of climbing the walls. Plus you need her support. In fact ask some of the longterm vets before settling your mind. This is important to your quit dude! Nonetheless I am quit with you man.