Wait, wait, wait. You take this girl out often, pay for her all the time, and you're NOT already a couple? What the hell are you thinking! If you're not locking lips with this girl you're nothing but her stooge.
Okay, let's get things sorted out. You're already like a boyfriend to her because you're always taking her out, you know everything about her, and she knows everything about you. The only thing missing is the intimacy and that's why you're stuck as friends.
If she's harboring a crush on you, that'll make things easier. Take her out less often but make the dates more special and personalized, i.e: you're putting a lot of thought into them. Then, at the end of the date, just go for a quick kiss on the cheek. I would avoid confessing, its better to let your thoughts be expressed in body language.
If she's not really into you, boy howdy is it gonna be tough. DO NOT confess under any circumstances. You need to withdraw from her life and start acting like a romantic interest. Go down the traditional path of dating.
You'll be able to tell whether or not she really likes you on your dates. If she talks and acts around you the same way she talks and acts around her friends, she's not into you. How much do your dates feel like dates? As in, how much does it feel like you're interviewing each other as a potential partner?