@Devin James man oh man what a question! I was asking myself this exact question not too long ago and I appreciate you sharing with the BP community as it is a very personal one. There's so much solid advice already given, but I just wanted to share my experience.
My wife and I were together 4 years before we got married, we pushed back just about everything we could. Wedding, ring, house, nice cars and anything else remotely expensive. When we started we had no savings, credit card debt, large student loans and terrible credit...We sat down and had hundreds of discussions as I educated myself in real estate, finance, and everything self help. She was hesitant to jump on board, but eventually she saw the "light!"
Now we own a 4-plex, a commercial building, purchased a profitable daycare center and looking for another plex or small multi family. We live off a portion of my w-2 income save the rest and the income from the properties and business we don't touch. I paid cash for her ring about the same price your girlfriends searching for and she's crazy about it! Next year we'll be able to have the big family wedding she wanted for years. We are by no means wealthy or financial free, but we're on the right track.
The truth is that everybody likes nice things and girls like diamonds, but buying liabilities before assets will have a negative affect on your future for years to come. Talk to your girlfriend introduce her to the site, listen to some podcasts together...BP's Money, paula pant's afford anything, and chose FI are great podcasts.
Best of luck to both of you!