If you live in the Dives, it's entirely likely that she might know you at least in passing. If you're Resistance, you're not going to know that Agatha is in the Resistance, unless you were/are in her cell. But you've most likely heard rumors of "Granny". I'm also always open to building back history with characters if you want to make a character that's an established Resistance member or has family in the Resistance.
I am open to building some drama into her life, though. If you have ideas for how someone would be an antagonist of Aggie's, you're more than welcome to shoot them my way! Just be aware that I'm very protective of Aggie and am unlikely to put her in a situation where she can get seriously hurt or even killed.
26 Vortas 2718: Aggie finds Gale in dire straits
20 Intas 2719: Agatha gets a visit from an old friend.
6 Hamas 2719: Aggie comforts the community in the aftermath of the Dorhaven Massacre.
20 Loshis 2719: Aggie meets the new Seventen that's been assigned to keep an eye on her.
13 Yaris 2719: Aggie's had enough of Jon Serro.