Why a girl I have sex sometimes say to everyone in night out I am her boyfriend?

I met this girl a month ago on Tinder and have already had sex with her three times. Honestly, I'm not very attracted to her, but I have a high libido and wanted to have sex. She herself said she didn't want a serious relationship. Yesterday I went out with her at night to a bar and she told a lot of guys and girls that I was her boyfriend. Why did she do that?

Why a girl I have sex sometimes say to everyone in night out I am her boyfriend?
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