I parked by a fire hydrant and her car insurance only wants to pay 90% even though it is her fault 100%.?

Tell YOUR insurance company about this. They will take care of the negotiations. This IS what you pay THEM for. And just for the record, they are trying to fleece you. But, if they report this, you will be cited for illegal parking and will have to pay a fine. But, like I said, let your insurance company handle it.