I invited a girl on vacation with me her mother never said yes now i want to take another girl I don't want to hurt her feelings what are some good excuses to make sure i don't hurt her feelings?

First of all, her feelings are going to be hurt because you asked someone else to go on vacation with you. This will make her feel dispensable and if you really like her, asking a different girl will definitely not make her want to be with you. I really don't think you should take this other girl if you originally wanted to take someone else. She will feel like a second choice and her feelings may get hurt as well. Why not take a guy friend with you on vacation? I can guarantee there will be less drama and perhaps the two of you can meet girls at your destination.