Hi OwlReally. Don't hate yourself or beat yourself down. We are all human. Sometimes we have fights, especially with people real close to us. If you have sent her messages apologizing (even if it was her fault you lose nothing by apologizing) that may be the best you can do for now. She may need time to cool off as someone else said. But if you two have been this close for 15 years I don't think the friendship will end in one hour. I liked the idea somebody suggested about finding a neutral place where you two can talk, when she is ready.

I agree about giving her a day or two to cool off, then try to reconnect.

You are not a bad person. We all have arguments and disagreements from time to time. I believe this can work out. Best of wishes.