Well first I can say "I feel your pain" we just returned this morning from our trip and my MIL went along, and as always was a major pain!
My hubby doesent say much, likes to keep the peace, I on the other hand will snap back. I forwarned my hubby that I will "play nice"

for the sake of the other 8 people on our trip.............BUT.........I do have my breaking points so I am sure that at some point on the trip......"its on" and it was!!!
The first day she started with the, its hot, how far do we have to walk, we have to wait how long,

all of which I told her many many many times before the trip, but she still likes to whine.
The second day in it really started, like we knew it would, but we did ask her to go along knowing it would have it bumps to say the least, (we pleaded temorary insanity to everyone else on the trip mostly my family) but I just decided early on that we were going to go on with our plans, do what we wanted when we wanted to and she either came along or didnt and needless to say she was in her hotel room alot,

all the better for us!
I kept my cool for awhile and after hours of her whining and complaing she says (for the 5th time in an hour) "I would never come back here" I calmly turned around and said "dont worry you wont be asked again" I got a ........big "hump" and a "well I never" and it was soooooooo quiet after that!!! everyone thanked me!
So I say tell her once, nicely, but firmly! Just like a misbehaving child!
Dont let it ruin your trip, like I told my hubby "we worked long and hard for this trip and I want to enjoy it....even if your mother comes along"!

and you can always look at it like this, the way I am right now, I can plan my next trip knowing she wont be coming along
