How do you know if a girl is using you to get to your friend because she is interested in him or like?

she'll probably ask u stuff about him all the time. when your talking to her, and she see your friend, notice her attitude.. she might change, but just because she changes, doesn't mean she's USING you. when a girl likes someone, they cant help but change. you just have to see, if she kinda 'pushes you out to the side' when he's around. or talks to you more [to maybe make him jealous] THAT is what u call using. when he's around, look at how she looks at him. also, best thing to do, is ASK her if she likes him that's the only way you will know