Hey Flash!
Diamond Bob and Barry are right on. Find out if she likes the pear cut first. Personally, I love them, but I am pear shaped too. LOL
Check out the dimensions chart, then go "Maulling" and look at your local B&M diamond brokers. You are not likely to find a lot of pear shaped diamonds to look at in most regular jewelry stores. Round brilliants are the classic and square cuts are very chic right now. That will help you learn about color, clarity, and you'll get an idea of the sparkle. You won't know how truly great any diamond can look until you see a really well cut one. Note Rook's comments on their experience shopping for a pear cut.
DO NOT give anyone any money!!! You might get pressured by some type of sales tactic like, "Someone else is considering this diamond." Don't fall for it. If that one sells, it wasn't to be, and another similar diamond will come/be available elsewhere.
Make notes about information you want answers to, come back to the PS forum, and post your questions. Be sure to keep track of prices you are quoted and compare similar carat weight, color, and clarity by searching PS vendors.
Think of it as car shopping, sorta. You decide on the make and model of car you want, but you don't run out to first dealer you come to and buy the first car you find. You might get a better deal (better price, more options, bigger engine) at the dealer down the street. Same thing with diamonds. Larger carat weight, higher color, better clarity, much better cut, same or less money.
Good Luck in your search!