My friend has a boyfriend but flirts with my crush?

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. She was talking to him and he was telling her that he likes me and trying to set her up with his friend.

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? Later on in the evening, he invited us back to his house, and she began flirting with him in front of me. She sat herself next to him and began trying to touch him up and threw herself at him saying "you can take me to a hotel if you want". I just acted chill about it. When we were about to leave, I gave him my number, then immediately afterwards she went to him and gave him her number as well.

I confronted her about it when we went home and she denied it and said “why would I do that I have a boyfriend?” And said she was only trying to “wingman me.” She looked really guilty but wouldn't admit it. Is she a snake?

I’ve now found out she’s added him on socials as well a week later and has trying to message him.