She could shut off the valve underneath the toilet which would stop the water from reentering the tank. If she needed to use the toilet she could either turn the valve on long enough for the tank to fill and then flush the toilet. or she could flush the toilet by quickly pouring a full bucket of water into the bowl. She will need about a 2 or 3 gallon bucket which she could fill from the bath tub. Once she fills the bucket she needs to quickly pour it all into the bowl of the toilet which will cause the waste to flush. She can then add a little bit more water to the bowl by slowly pouring in about half a gallon which will bring the water level up to the normal height.
This message has been edited. Last edited by: Cutinzs,
"IF" by chance there does not happen to be a shutoff under the toilet and there is a float ball rather than a fluidmaster valve, she can wire the float ball rod up so it does not drop down and cause the water to re-fill the tank. Either tie it up with some dental floss and a weight over the side of the tank, or prop it up someway.
The fluidmaster float could also be propped up from underneath to keep it from dropping and attempting to refill.