Am I overthinking this situation?

So my bestfriend is female and I've had feelings for her ever since we started talking. She says she would be happier as friends than in a relationship. Well things happen and we don't talk for awhile. Long story short, she never told me about her new boyfriend she's had since mid December 2019. I found out the end of January. Would there be a reason she never told me?
Am I overthinking this situation?
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