Not sure if she would accept your proposal

The saddest thing is to have to return the diamond ring you bought to the jeweller because the love of your life turned down your wedding proposal.

Maybe she's not ready to settle down yet even though she loves you. Or the time is not right. Or she isn't sure of her feelings... No matter what she says, it sucks. So what do you do with the ring?

Better play safe. Feel her out before you propose. While chatting, bring up questions like.. what if? Would she ever want to settle down? What are her feelings about starting a family? Or would she just want it to be just the two of you. Can she imagine being with you for the rest of her life? Can you imagine waking up to her face and voice every morning?

Still not sure if she'd accept?
Maybe she loves cartier, but right now, you can't afford it. Maybe you can but if she turns down your proposal, it'll mean money down the drain.

Get her this.

Cartier -esque Inspired Cubic Zirconia Solitaire Engagement Ring w/ Channel Set CZs
Bring it with you when you have that what if chat.
If she accepts, you have something beautiful to slip onto her finger. Tell her you'll get the real thing first thing in the morning or when you can afford the real thing.