When a lady is angry at me, should i leave her alone?

is a long story but make it short. there's this lady that i'm in love with, where in our early 20s, when the first time i met her, it was all fun, wonderful times, until little by little, she was changing, it's been two years that she changed (for example: every time i see her she gives me a cold shoulder, doesn't say hello, nor goodbye, instead of talking to other friends, tells me a liar). But on Monday, that's where the ice burst, when we were talking about party planning, out of suddenly she started to be rude to me, giving me a cold shoulder, while her cousin, nicely responding is a girls night out, and i respect it her. but then it gets better, then i speak to the angry girl, telling her what bothers her over me? what can i change it? she was silent, and me bitterly sad, then she broken my heart while she said "we should had been good friends." so i decided to leave, and instead of being in pain, i know she's been mad over me since years, what's the plans, leave her alone, or forget her? any helping tips!!