Engagement ring help?

Sounds like she knows exactly what she wants. If you're budget-minded, you can always start off with a smaller gemstone, and "graduate" to a larger one further down the road (maybe even 1 year anniversary, for example). Huge rocks aren't necessary, especially if she's got small hands. You can do one of 3 things--talk to a jeweler and see what he/she recommends (don't let them pressure you into buying, though). Second thing is to take your girl's friend(s) with you to the jewelry store and let them help pick out what she would like (if they're close, that is). Third option is to take her mother to the store for help. :)