I feel like the worst person in the world right now

thats kinda messed up... but if u were actually best friends i think you could fix it up.

id give her some space first of all for a few days before i tried to expalin myself again. id just tell her that like you said, she didnt deserve any of the things that you said and that you feel horrible about it because she is one of your best friends. tell her that you only said them because for a little while youve had some feeling for her and you seeing her with someone else bothered you and you got jelous and stupid about it and shouldnt have taken your own issues out on her and that your really sorry and hope that you can still be friends because you really do enjoy being her friend.

see what she says and make sure your honest about what you say. she probally wont be 100% ok with it after that and things might b awkward for a bit but if you both really want to work on it and still stay friends then i think it will work out. also make sure that you tell her that you know that she doesnt feel the same way about you and that your ok with that now, which will help with a lot of the awkwardness... good luck bud! its worth a worl!