Jade Holt's speaker has just been left, and she answers the hurt with sarcasm. The repeated line "Sure, go ahead" sounds like permission, but it really works as a dare. She is pretending not to care while making it clear how much it stings.
The poem suggests that the speaker has been replaced. The line "You said I was / And now she is too?" hints that the partner once called her the perfect girl and is now saying the same thing about someone new. That repetition makes her compliments feel cheap, and her own sense of worth drops with them. She calls herself "last night's empty bottle," something used and tossed aside, and she guesses she "wasn't worth your time."
The image of "Forever" being cut by "a dagger fashioned of ice" is cold and sharp at once. It suggests a betrayal that was quiet and unfeeling. The mood is raw and defensive: anger and heartbreak sit just beneath the sarcasm.