D - being her friend is good. It puts you in a good position to DB. But, don't do it forever. Do some thinking about our earlier exchange. Maybe approach it after the first of the year. She needs to realize that this limbo needs to end. So do you.
Be unavailable once in a while, D. Decline an invitation. Don't answer the phone when she calls. Delay texting as long as you can. Be a little mysterious. Talk about a new friend...your friend Judy who also raised boys. Just a friend you met online through other friends. Use any name you like...I'm trying to help you knock her off her comfy perch without lying. Nothing wrong with making friends.
Shake that woman up, before you wind up in the friend zone forever! She's getting into a rhythm. This is not the goal you want to reach, right?