I am afraid of pushing her into OM's arms by making her feel like I won't ever forgive.
The reason she's with the OM has nothing to do with your demonstrating forgiveness now.
If I don't do anything, does it reinforce that feeling?
You mean as in not giving her a gift nor a romantic card? Nope.
You are assuming a couple of things, it seems. That sending her a gift shows forgiveness; that said forgiveness not being shown is an impedient to her returning to you.
If you were to have the mind of a WAS, you'd see it quite differently. If you give gifts or sentimental prose at this time, that will more likely make her uncomfortable, or make her sorrowful or make her feel guilty. What you'd like to do says more about the way you're feeling then it does her; it's giving you an emotional vent.
But I'm hesitant to say don't give a small gift if you really, really want to, just a little something you know she'd like. Use your knowledge of her to make the gift appropriate and personal, meaningful. In that department, you're one up over the OM. But don't expect or hope anything to come out of it, keep your expectations at zero.
Tormadoes, I tried finding your past threads and you have quite a few, but never finish them. A suggestion for you: finish one at a time. It makes me so much easier for others to find 8 or so pages of posts in one place and follow along the progression of events and comment accordingly than to have people forage through multiple threads to keep up... which they're not likely to do.