tell her ,
COME AWWWWWWWNNNNNNNNNN MAWWWMMMMMMMMMMM
start crying and screaming and procede to go into fetal position.
simiilar circumstance happened recently to me, except it was like 15 smashed kids that spent the night. glad i got a bed if yanawadimean. claim/
just be straight up like her moms fine with it, we wont be in the same bed (sneak in at 2, leave at 3 if you can last that long) and its no biggie. if that doesnt work nothing will, except maybe a beating until she breaks.