I truly apologize, I thought I thoroughly read your post, but I was also making dinner, doing laundry and dealing with 7 year old driving me nuts. I'm not as good of a muti-tasker as I thought I was.
Your woman sounds pretty serious about you. But if the thought of your ex showing interest would make your life turn upside down, you might not be as serious??? I'm not going to tell you shouldn't be in a relationship then. I'm not like that. But this may get messy if you still don't know what you would do if your wife shows interest.
This young lady most likely wants kids and a husband. Might want to have that talk with her.