I'd arrange at least 30 minutes to get through security...

I haven't been out on a Friday morning in the past few months, but there are obviously bound to be much more people there than on a Saturday.

The good news (at least that I feel) is that you should have options at least: if the security is bad or looks like it will be (with hordes of people on UA) on the 'west' (UA) end of the terminal, go to the other end and go through security there - i've done it a lot of times and have had much better experiences.

Plus, if you and/or your neighbor is a 1P/etc, you should have access to the slightly faster lines for security.

Finally, your best option perhaps is the Dulles Diamond line near the Baggage Claim, between 8/10 if I remember correctly, which hopefully won't have many people - just beware that all the handicapped/wheelchair patrons go through this security line too.

Enjoy your trip!

-jeremy