How can I get rid of another girl flirting with my crush when she only wants to use him?

I have had a crush on this guy called Matt for a while now. He is really cute, his smile makes me melt. We are friends but there is flirting between us. Everything was going good, for a moment I felt like he liked me too... until this girl named Evie came swooping in.
Evie is known for taking and 'stealing' people's guys and using them to create a good reputation for herself. She flirts with guys and makes them falls helpless in love with her when she doesn't care bout them at all. Then she ignores them afterwards and leaves them hanging begging for her to go out with them. she always says no and keeps doing this cycle.
She did this to my previous crushes and ruined everything between us. Now I feel a real connection between me and max and she comes in, flirting with him... laughing and talking with him, wearing very showy clothes and bending down in front of him.. JUST TO USE HIM. I feel betrayed by her, jealous and sorry or matt all at once.
HOW CAN I STOP THIS. I cant tell matt the truth because she is sorta my friend and everyone will start hating me and I don't want to cause so much drama in my life. :(

If the guys you're interested in are all incapable of resisting any girl that flutters her eyelashes at them, the way to stop it is to reconsider your choices in guys.

Dating and relationships aren't a competition. It's the process of finding the right person and building a bond between the two of you. When another girl comes around and your guy goes for her, that's mother nature saying loud and clear, "He's not the right guy!"

The object is not to defend your boyfriend against all of the other girls in the school, it's to find a boyfriend with enough maturity and loyalty that you don't have to worry about it.

It's hard so slap that damn slut in the face

How is she your friend if she keeps taking guys away from you? you know, just let her get what she wants and maybe forget about matt. yes, it's gonna be hard, but try. or she be like, “so and so is causing trouble!” which you are not. hoped this helped.