Aww I would totally be up for her and Joel knowing each other. She'll always want to be a good friend to someone she meets and thinks is a good person at the end of the day.

She passed away in 1998 so for a good seventeen or so years. The coffee shop has been around since the early 2000s so I can definitely see them knowing each other for a while. Let her talk to you about what all the young ones have been chattering about at lunch, Joel, and let her hear you talk about whatever you want or just enjoy each other's company. Whichever he prefers more.