I admire your positive thinking but when a girl doesn't want to be alone with you, that's a BAD sign! Go if you want but I predict you will not achieve anything with any of these girls tonight and when you come home after the "date" you will feel very disappointed and frustrated. You'll be wondering: "I got fvcked over, why was she flirting with me last week but acting distant tonight? I thought she liked me but she doesn't, so why didn't she just tell me instead of meeting up with me tonight? Life's not fair, women are evil, boohoo!"
Well, she DID tell you! By saying she's bringing a girlfriend along! So fvck this bytch and spare yourself the frustration. Just text her: "Sorry, something else came up so I won't make it tonight. Have fun, though!". Then go find another girl, one who wants to be alone with you!