
Oh Step3, so sorry you feel this way. I can understand you are upset. Breaks up are not easy. And over little things like that? It is possible that she just needed validation from you that you care. It seems exaggerated for us. It is also possible that she is so scared of abandonment that she prefers to sabotage relationship. I am not an expert, but maybe she got scared of candle dinner (very nice romantic thing). Maybe little things she asked was like a test, something she asked, not you offered,to see if you could fulfil it? And you didn't on time (according to her) so she had a reason to break up. I am just trying to imagine what she might think and feel.
Is it so important to be right for you? You didn't forget those things, but does it matter? She felt betrayed. Could you just say something like: I am so sorry darling, I didn't realise it was so important to you. I got you your favourite desert, shall we eat it while choosing a movie we would both enjoy?
There are people here, who can give you great advices on how to handle conversations, I am sure someone will help you out.
Have you read about BPD relationships? Ways of communication? It is helpful to see how other one thinks. Have you noticed a pattern when she acts out of proportion? What makes you think she has BPD?
Meanwhile, to ease your pain do something to distract your mind. So you can calm down and think clearly.
Keep writing here, it helps
D.W