Why are some girls so possessive over their guy friends when it comes to the guy liking another girl?

Anonymous
This guy and I liked each other for a while but he seems very unsure of what he wants. He is close friends with some girls that we went to college with. I barely know these girls and I know he’s been talking to them about me. The one girl seemed very supportive and she even told me how sweet of a guy my crush is and everything, just like a wingman. She called me his girlfriend a few times too. The other girl my crush hangs out with is married and she seems more possessive. She mocked me while I was in the same room which made my crush feel uncomfortable and he told her to stop. She brought up his ex girlfriends while I was around which he said to her “I don’t want to talk about it when (my name) is right there”. I’ve heard my name come up in their “private” conversations when they thought I wasn’t listening, usually it’s her talking and him saying not to talk about me while I’m in the room. Things like that. Her and I have quite a few mutual friends who all say she’s a nice girl but she never gives me the time of day. Every time I would see her, she would give me a smirk. She told my crush that if he ever gets a girlfriend she’s going to steal her from him in which he didn’t say anything to that. She said that loud enough for me to hear too.

She’s been married for over 10 years. Why is she so protective over the guy I like? I feel like she maybe part of the reason why he’s being a little distant with me.
Why are some girls so possessive over their guy friends when it comes to the guy liking another girl?
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