Here's my take on this
First of all, what does she mean by the 'real thing' - Does she mean 'the one'? Does she mean 'officially bf/gf'? Does she mean real thing = will be the first guy she sleeps with?
From knowing this chick as you do, what does she mean by 'the real thing'?
How invested in you is she? Have you guys hooked up? Do you share a social circle? How does her social circle compare to yours in the 'hierarchy' of it?
Now I'm gonna throw in a a couple 'IF's.
If you have hooked up with her, then she probably sees you as more of a casual hookup than bf material - to fix that you just need to flip more 'care taker of loved ones' and 'ability to emote' attraction switches.
If you have not hooked up yet, then she is probably considering you to be tossed into the friendzone - to fix that, build attraction (DHV, Neg, ramp up Sexual Tension, make her jealous)