You’re in a long term marriage that’s feeling a little stale, and you’ve contacted your first love who is divorced. Now you’re fantasizing about what life would be like if you were with her — and not your wife. Lots of people have this type of fantasy and curiosity. Marriage takes work if you want to sustain it, and there are all kinds of temptations. What you have to do is decide if you want to stay in your marriage or not. If you do, then you need to work at it. If you don’t, then you should get out of it before you start dating anyone else. It’s not fair to any future girlfriend, your wife or yourself if you create drama by dating during marriage because you want out. Just walk through the exit door, get divorced and then date — if that’s what you want.
As for your ex, she’s not a friend and if you see her without your wife, it’s going to be a lot more like dating than like friendship, so make sure you’re clear on that. Your feelings towards her are not friendly. They’re romantic. So, make a decision about your marriage — in or out — and then if you stay in it, and want to connect with your ex, invite her out with your wife, to minimize the potential drama.
I hope that helps.