If she had waited any longer would the Pit have even worked? Everyone is telling her itayumi have been too long and you think the solution was to wait longer? Maybe she waits a few weeks or months and learns about Constantine only for the Pit to fail at even reviving Sara. Or the Pitt revives her in a state even worse than Sara is in now and even Constantine doesn't have a way. When your told it may already be too late you don't have the luxury of sitting on your hands. She had the opportunity to save her sister she took it. It didn't work out too well but sometimes that happens we you take a chance. Right now she's taking another chance, can she find a way to save Sara. That decision will also have consequences. But the decision not to use the Pit also would have had consequences. Sara dead...permanently.