Must suggest that you find out what she wants. There's nothing worse than a woman who hates her engagement ring. (I know plenty of them)
You might also try asking if there is a ring that's been passed down from generation to generation in the family. Lots of families are like that. Typically if a single woman has owned the ring and is going to pass it down to your girlfriend it may have enough metal for a plain setting on the engagement (where the rock is!) ring and enough metal left over for the wedding band. This is an awesome way to go: a. because it's got family ties to it. and b. all you'd have to pay is the re-setting fees.
