HELP ME IT'S URGENT OMG!?

k so the guy I like and me r friends but there is this other girl who says she and him are so called "bffs". I find her as a threat right now if me and him start going out. I don't know her that well, but can't determine by how they act when they're near eachother and how they talk on facebook if he likes her instead of me. I am worried because I don't want Mackenzie (her, the threat) to steal Jordan (him, the guy I like) away before I can do anything. HELP, please. I don't know if I should be doing something I'm not. Thanks.