Why people do they despise same one if he have sex friends?

I have a neighbor who she is about 25 y. o I met her yesterday and we talked a little.
She told me how is your new relationship was,
so I told her that I am not in a relationship, but that she is just a sex friend without emotions,
and it seems that she was upset about the matter.
This morning I met her and said good morning to her, but she did not answer me and kept looking at me and give me eyes contact for 4 or 5 min
What does that mean ๐Ÿค”
Why people do they despise same one if he have sex friends?
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