Unless she said to you "I don't want a ring," chances are pretty good she does. Remember that she's the one that has to wear it her whole life, so you should make sure whatever you end up giving her is something she'll actually enjoy wearing...every day, for the rest of her life (God willing).
If you do end up resetting the stone, spend a decent amount of time finding out what kind of settings she likes. When you pick out the metal for the setting, go with what jewelry she wears (yellow or silver colored). Also do some research on the pros and cons of each metal. Platinum is stronger and rarer than white gold, for instance, so it costs more. But white gold needs to be replated to stay white and is more prone to bent and broken prongs, so these are all things you need to consider. Good luck!
I was on a bit of a deadline; we we had a settlement on a house looming and we'd sort of agreed that we'd be officially engaged prior to signing the papers. I formally proposed w/ a nickel-plated antique boy scout ring I'd found someplace ages ago. (it was a big week - I got engaged, bought a house and a used Ducati 900SS) We than discussed what she wanted, and I used my sister's connections in the diamond and setting trades (she owns a neat silver shop in Yellow Springs Ohio) to get the setting cast in platinum. The diamonds came from NYC to her, she shipped them to me for approval, and I sent them back to her to have set when the metal was finished. It turned out very well; totally understated and a one-off piece. It ended up costing about 60% of bargain retail, and the money saved was invested in the (now ongoing for 10 year) renovation.
My unsolicited advice to a starting couple is: Don't sweat the little money things, it all evens out. Try to save on the big stuff though. Also, from day one we've had a common or house account into which we both pay on the basis of income. If one person makes 1.3x what the other does they pay 1.3x as much. It goes in via direct deposit and the mortgage auto-debits. Big expenditures come out of there. We both still have our own money in our own accounts, and our own credit, investments, retirements accounts, savings, titled vehicles, all that.
We've never had a disagreement about money, probably as a direct result.
I guess I got lucky. My wife is a huge advocate of clearance shopping. I asked without a ring, and one day we were walking by a clearance rack of jewelry and she stopped and pointed to one she liked. So I grabbed it and took it to a jeweler she'd used for years and had it sized. Unfortunately our rings got stolen a year after we were married. we both worked for the same restaurant chain, I went to pick her up one night from work, and as we were leaving they got slammed, of coarse being the "responsible" managers that we were, we jumped on the line and helped them push through it, we took off our rings, and put them on the band of my watch, and then put them on the desk in the office. Forgot about them, next morning when she opened up and we looked for them, they were gone, and NOONE on shift the night before had seen them(of coarse). A year later we've both got new rings, and she seems happier than ever with her new ring. Again, a clearance ring, with a nice ring jacket. I went without till last year, she got me a tungsten band for my birthday.
Her comments on this thread were this, ask her parents, and depending on your girlfriend, get her opinion on the ring, "I'm sure you have talked to her about it"
Maroon, IMO discussing your intentions with her father and stepfather, separately or together depending on the family dynamics, goes a long way to show that you're a stand-up guy, not rushing into things, planning to take care of their little girl, etc. living together first, as DILYSI pointed out, takes a little of the gallantry out of it, but telling them of your intentions and asking for their permission is still a righteous thing to do.
i like the idea of using the heirloom stone in a new setting that you design or select. but if money is really tight, i wouldn't hesitate to propose with the existing ring. if she wants to do a remount / redesign, then that's something you work towards together.
Congratulations on finding someone who makes you want to go through all this! I'm coming up on 10 years, two beautiful daughters, and i wouldn't change a single thing in my life. I wish the same for you.
I've had my 1/3-carat engagement ring for close to 30 years, and wouldn't think of changing it, though a (still teeny) 10-year anniversary band did join it along the way. That's me, though; I've always had bigger priorities than a rock on my finger, and I did get to pick out the stone and setting, so it suits me. Takeaway message: Ask your girlfriend. Settle on something together.
It's good practice for the many, many more important decisions you two will be making together in the future.
Margie
I offered my wife my mothers wedding ring, but she was worried about breaking it (it had an opal instead of a diamond). My wife already knew it was coming (I had discussed it with her and her family often) so we went ring shopping together. We went to a few places, and we hated them all. Gaudy rings and pushy salespeople. (Here comes the commercial) Then we went to Zales. I have to say, I will be using Zales for the rest of my life. They where really friendly, well priced (her ring was $750 IIRC). The had a lot of options, and didn't try to push us into higher priced crap.
So uh, I'm not sure what I'm suggesting actually.
GI_Drewsifer wrote:
I offered my wife my mothers wedding ring, but she was worried about breaking it (it had an opal instead of a diamond). My wife already knew it was coming (I had discussed it with her and her family often) so we went ring shopping together. We went to a few places, and we hated them all. Gaudy rings and pushy salespeople. (Here comes the commercial) Then we went to Zales. I have to say, I will be using Zales for the rest of my life. They where really friendly, well priced (her ring was $750 IIRC). The had a lot of options, and didn't try to push us into higher priced crap.
So uh, I'm not sure what I'm suggesting actually.
I haven't gone to Zales yet...
Been to Reiss-Nichols, Jared's, and Shane Company.
I wish i could get off with $750. 
I've lived with my girlfriend for 3.5 years. We bought a house together all that time ago and are still doing well. She wants a (Miata key)ring. 
93celicaGT2 wrote:
GI_Drewsifer wrote:
I offered my wife my mothers wedding ring, but she was worried about breaking it (it had an opal instead of a diamond). My wife already knew it was coming (I had discussed it with her and her family often) so we went ring shopping together. We went to a few places, and we hated them all. Gaudy rings and pushy salespeople. (Here comes the commercial) Then we went to Zales. I have to say, I will be using Zales for the rest of my life. They where really friendly, well priced (her ring was $750 IIRC). The had a lot of options, and didn't try to push us into higher priced crap.
So uh, I'm not sure what I'm suggesting actually.
I haven't gone to Zales yet...
Been to Reiss-Nichols, Jared's, and Shane Company.
I wish i could get off with $750.
If you can't off with $750 I think you need lower class company. Just saying
