I hope I'm not dampening your spirit here but it's hard to turn back once you've started...
I chiong-ed for close to three years before waking up and realizing that all these are just a waste of money...
I guess the easiest litmus test (tested and proven) to confirm if she really loves you or just your money is to see how much you have to spend on her. If you find that you have to buy flowers or LDs for her, pay for all her meals (including the times she brings her "sisters" and "brothers" along hahaha) and basically everything else, the alarm bells in your head should be ringing already.
I've met many friends who don't spend a single cent on their siam bu... Maybe just small things here and there but never hang flower, never buy drinks, nothing. And the siam bu stays with them everyday. This may not be enough to show that she's sincere but at least at the end of the day you don't end up with a broken heart and an empty wallet, right?
Anyway it's not that sincere and genuine girls don't exist, but they are rare and hard to find. You're lucky if you can find one, but don't go searching for one.
My advice would be that it's ok to play... But make sure they don't treat you like a carrothead.