I have also noticed these similarities and I love that someone else has too. In my mind I actually picture Shallan looking like Anna. I hadn't thought of Siri and Vivenna but I totally see it now!
I'm a mom of two young children (1yo and 3 yo), married and working full time. I have no time for reading anymore but I spend 1.5 hrs in traffic every week day. These audiobooks are what keep me sane.