Why would a girl I rejected, spread a rumor to everyone at work that I rejected her?

Anonymous
At work, i know this girl at the reception for the last 2 years and a month ago she approached me and asked me out on a date. I rejected in a polite manner away from everyone and told her that i am not willing to be in a relationship because i am committed to my work and post graduate studies. I told her that i appreciate her coming up to me. Everything was going fine until people started acting weird to me at work... especially the other women and know they feel like i hurt her... i don't understand what i did wrong?
Why would a girl I rejected, spread a rumor to everyone at work that I rejected her?
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