I said ily to another girl that isnt my girlfriend, my girlfriend got mad, (read story)?

Well ive been there and done that (kinda) Well just sit her down, be calm and tell her you didnt meant it as anything more than a friend. If shes mature about it she'll listen, if she isnt then just dump her. Trust me dude, her doing this just shows her insecurities, she probably wont ever trust you, no matter how much you try.