I only speak the truth. :) It's a hard and cruel fact but there are times when our fish die suddenly and for seemingly no reason. With other creatures and even with larger fish, we can examine them, take xrays or biopsies to get answers but with bettas, often the only way to pinpoint a cause of death is to do a complicated and expensive necropsy. In a case like your little Lisa, who died so quickly, there are chances that even if we found out the cause of her distress we would not have had time to effectively treat it. That's the problem with internal issues. Often the symptoms don't appear at all or if they do, they appear too late.
You did the very best you could and I'm sure she was a happy girl who knew she was loved.