Why did my friend flirt with the guy I’m interested in?

My close friend kept encouraging me to go after this guy I like because he’s told her and other people he likes me as well. She has a boyfriend and was giving me some “tips”.

So I went out with her clubbing and we met up with him, and he was trying to kiss me and we were talking all night. So tell me why does my friend suddenly start flirting with him too and tries to give him her number in front of my face?

I confronted her about it after and she denied it and said “why would I do that I have a boyfriend?” And said she was only trying to “wingman me.” Is she a snake?

I’ve now found out she’s added him on socials as well and has trying to message him.
Why did my friend flirt with the guy I’m interested in?
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