Some people hate to say negative things.
I have had various parties over the years ~ for birthdays, Christenings, etc, etc, ~ and I am always surprised at the number of people who do not intend to come, but simply will not respond, or say that they are coming, but don't turn up.
It's annoying, because money has to be spent on meals for no-one and, where numbers are limited, it means that others cannot be invited.
This may seem irrelevant, but, after reading about the number of people on here, whose partners have said that they still care, but are unsure, and just want to be friends for a while, only to end the relationship completely, I have come to the conclusion that these are the same kinds of people. They just cannot say what they mean. They cannot bring themselves to say something 'negative', but what they do do, instead, is far more negative and unpleasant that the truth, in my opinion.
It's not fair of her to be angry with you for not understanding.
If you read some of the other threads, you will see that you are not alone.
Time will heal your pain and you will find someone who will honestly want to share your love and your life, long-term. Then you will be grateful to this girl who has let you down.
Good luck
