10Know: She Was the Last Person Felicity Called Before Her Possible Demise
Roy, William, Dinah and Zoe found Felicity's bunker, and William hacked into her system. He brought up the last file she accessed: structural maps of all the buildings in Star City and schematics to build explosives. It looked like a plan to level Star City.
William then looked into who she
contacted last. Felicity's last call out was to Blackstar, a.k.a. Mia Smoak, her daughter. She clearly was protecting Mia's identity from whoever may have been able to access her files, despite the security protocols she put in place. It may also be of importance that someone named "MC Queen" was listed on Felicity's call log.