Mixed signals received?

Hi I'm looking for help with a woman known for a little while but only made brief pleasant talk and introductions in past few weeks. In same circle she gave nice smile and nice chat a few times. Introduced myself then another week later wished her happy birthday when found out what day it was. Appreciated it. She has made consistent eye contact with me over a period of 3 months or around then, I thought this way a subtle sign signal if I'm not wrong? But then the following week, said hi again but she responded with brief abrupt hi.. then from then forward has suddenly avoided eye contact with me and looking away not smiling. Used to sit near me but not now. Can someone wise enough please help me, as I don't know what to think now about this woman going from super nice friendly smiles and lots of eye contact , to this cold harsh avoidance of me. I don't believe I did anything wrong by her , nothing intentional anyway. I'm quite introverted man but I made big efforts to initiate contact with her those few conversations. I don't know if I missed something or any signs but anyway hopefully someone here can help. I don't even know if she may have found someone else? Could be possible don't know. Anyone please help?

Mixed signals received?
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