Girl I know what your going through, and honestly it sucks!! Right now I live w/ my FH at his mom's house which includes his oldest bro and roomate (both 30+). I feed Ranger twice a day, but my FMIL has been putting food down for him whenever she sees the bowl empty. Her reasoning is that her friend at work leaves food down 24/7 for her chi

. She will even feed him people food while she's cooking (before I get home), even after I told everyone in the house not too.
The boys will also give him treats constantly whether he did the right command or not. So now when I say lay down he rolls over

. I have to practically start over and re-train him

.
I've even put notes on the fridge where everyone would see them. And still they don't do what I ask! I hate having to crate Ranger b/c people can't pick up after themselves. . .I just can't wait until we get our own place at the end of the year!!!
I would say the friend is "grounded" from coming over until he understands the house rules, that's what I would do for anyone that doesn't listen to what I say!! Good Luck!