Nadine Ohara - SF Bay Area/CA , Jul 27, 2009; 12:24 p.m.
Basically you mask the window and try to recover as much detail as is there. Same for the floor. If you use Lightroom, the adjustment brushes can work.
You 'could have' shot another frame that had the correct or close to correct exposure to the window and composited them. If you can go back to the church and do that, you might be able to do that still.
Otherwise, you could use flash on the couple, and possibly in the near background area (shooting up to the walls) to bring the interior/subject exposure up enough so that you could get some detail in the window. You probably won't be able to balance it exactly without the interior going black (as you discovered). So an 'in between' exposure that brings just enough detail back in the window that it doesn't look like a white blob.