A verbal--or more properly, oral--pledge to a charity is most likely not enforceable. The law does not enforce "gratuituos promises," or promises made by one party without there being any consideration (anything of value) offered by the other party, unless there was some signficant reliance by the other party on the promise, which there probably is not in this case. Also, if there was consideration--which would turn the promise into a contract--contracts are typically not enforceable if made by a mentally incompetent person.All that said, if this is legitimate charity (so, a good cause), the best thing may be for someone to simply pay the $25 on her behalf--that may end the situation with the least strife and difficulty.