"She's not friendzoned you, OP. You've girlfriendzoned her. Now then, it's a fact universally accepted that most dudes would bone their female friends given the opportunity- however, seeing a female friend only as a girlfriend is girlfriendzoning.
She's not rejected you, she's still your friend. She's just turned you down for a date. She's probably sitting at home thinking 'wtf, have I been girlfriendzoned here? Has this dude only been nice to be for the last 5 months so he could get into my knickers? Was our whole friendship a lie? HOW am t going to get over this?'
It sucks to be in the girlfriendzone, the more it happens the less you trust men. Seriously, it's shit.
Secondly, she's turned you down because she doesn't fancy you. She said it was because you didn't smoke because she didn't want to hurt your feelings, it was probably the first thing that popped into he head.
So, then, OP- what to do?
You need to remove this girl from your girlfriendzone. Let that shit go. Stay stoic. You can control how you feel, but you cannot control how she feels. Every time you catch yourself thinking about her, imagine her scratching her arse and sniffing her fingers, or picking her nose and eating the boogers- whatever it takes. For the love of God, do not start smoking to impress her.
Romantic rejection sucks, bro, but it's not about you, it's about her-so there's nothing you can do.
Now's the time for a little self improvement. Stop using the term 'friendzone', when women hear it we translate as "immature neckbeard with misplaced sense of entitlement" - it's not attractive. Dealing with any kind of rejection is a challenge, and challenges are what make us tough."