15 years ago, freshly employed, less than 25 years old, introverted and socially awkward, I had a work colleague as well to which I wrote a romantic poem (for her, more or less out of the blue). It wasn't received well. Not well at all. I had trouble understanding her dismissal and insisted on that she gave me signs of affection. HR was involved briefly, my story sounded so similar to what OP writes. But in my case, she quit the job. Years later, I realised my self-delusion.