PG writes about her influence here, and why she avoids the spotlight:

https://www.paulgraham.com/jessica.html

He also seems to give some credit to Jessica for choosing to back the Reddit founders:

  we thought that we were funding ideas rather than founders, we rejected them. But we felt bad about it. Jessica was sad that we'd rejected [them].

Edit: she gets mentioned here too: https://www.paulgraham.com/ycstart.html