If it is only your GF then I think you better leave her now, I know girls are crazy on those designer bags or luxurious items, but she ain't even your wife yet and she would drain your wallet like that?
Find someone that could also help you grow, those who have mature minds who could distinguish the difference of what they want, and what they need, who wouldn't just recklessly spend money, but have a plan or vision for both of your future.