Its an emotional affair and the secrecy makes it more appealing. You are infatuated and love the idea of her. Shes a fantasy, not reality.. reality with her would be hell.. both spouses hating you both, your kids heartbroken and angry.. and even if there wasn't those issues.. real life sets in to ALL relationships and it would just end up the same as your marriage now.. working, paying bills, kids getting in the way of normal sex life etc.
You are supposed to work extra hard at making your current marriage work.. not turning your attention elsewhere because life gets boring sometimes or the spark has faded. People who get infatuated like this usually are not thinking rationally and make really bad decisions that could have major consequences.
Do some research on emotional affairs, read the 99% failure stories.. not just the 1% that give you hope..
You are too close to her. Men and women cannot be that close without things getting complicated and messy. You need distance and a more professional relationship where you have your role, she has hers and you only come together for business meetings if or when necessary.. if this doesn't help you get over your feelings then its time to find a new job, get your priorities straight and put your family first.
Put all that effort into your wife. Take her away for a weekend, spoil her and work on getting the excitement back in your marriage. It may take time and effort but you married her for a reason and need to put her first
"Don't ask a question if you can't handle the answer".