used to be friends, then she changed, then she rejected me, what should i do?

i had a female friend who had just broke up with her fiance, i tried to cheer her up and taking her out of her depression, we became closer and closer, and she'd tell me about everything about her life, when she was sad she told me , when she was happy she told me , we didn't meet that much as we live in different cities, but we did it over text, and during that process i fell in love with her, .

but suddenly when she had a new job, she started to change, she started ignore me when i ask about what's wrong with her, and answering angrily when i insist on knowing.

i decided to confess my feelings to her, first my decision was to tell her face to face then i failed to meet her, so i told her over text
her response was : "thanks for ur feelings towards me , but i am not thinking into going into a relationship now and for a long time"
i tried to know why , she replied that she don't want to be emotionally and Psychologically attached to anyone. and she wished me to find a girl that deserves my love to her.
before i stop texting , i asked her to think about again , and she promised she will, last think was me hoping we will still be friends.

so why do u think she changed her attitude in first place, and what should've been my attitude towards that ?
and what should i do right now after i apparently messed it up ? should i talk to her again like nothing ever happened ? it is hard for me to let her go and move on, i want to know if there is an another chance