Some people will tell you not to do this and there are others that say they do it frequently. It's your choice as to who's advise to take.
My snake has refused a f/t rat before and I will only leave it long enough to find out she is not interested in eating. I will refreeze it and use it on the next feeding. If she refuses that same rat again it gets thrown out!! I only have the rat thawed for less than an hour before it goes back to the freezer. I have not had any problems so far. There is a post on here about reusing f/t feeders if you want to search it and read others opinions.
One other option is to buy another snake. Try to feed the fasting snake first. If it doesn't eat then simply feed it to the other snake that is eating! LOL!!