if you are close enough to her, just be honest! Tell her if it's at the house, she and friend are responsible for set-up and take-down - she probably hasn't thought about all the stuff that goes into hosting besides invites and food.
yeah, I get it. I would be the same way (although, you guys don't ever have leftover food? like, you always throw away the extra?) and often move things around because H will just put things in random places sometimes.
What about bringing it up and suggesting a change of location...like lower key but at a restaurant/brunchie place? Then you have to lug home presents, but no house cleaning?