First of all, welcome
Lucky girlfriend! I am sure she will be absolutely delighted!
To be honest, I think that's a lot of money for four nights. Where else are you thinking of going while you are in the US?
My next question: is there a particular reason you want to stay at the Dolphin? I only ask this because there is a chance that when the 2014 promotions are released in late April (which would be the best time to book for the best deal) that free dining will be offered. This is a maybe because nobody knows from one year to the next what offers Disney is going to have on the table for the next block of booking availability, but it's worth waiting to see first. If you choose the Dolphin (or the Swan) although you have the benefits of being onsite, you will not be able to take advantage of free dining and neither would you be able to use Magical Express from the airport and back again. I would think that this would be a big consideration for you if you and your girlfriend are both fairly young.
I personally find Virgin Holidays very expensive and prefer to book my hotel and tickets through Disney directly, and then choose flights when they are released which is approximately 11 months in advance of your return date. There are some package deals to be had, but you have to be very diligent (and a bit of luck is involved IMO) to find them.
Unless you want to do ridiculous amounts of shopping, $1000 would be a very nice amount of spending money if you don't have food costs to be taken out of that budget. Which brings me back to the hope for free dining .....
One more consideration for you is when you will be 18 if you aren't already. You would need to be 18 or over to book your trip as far as I know, unless you have an adult who you trust and who trusts you enough to enter into the contract for payment on your behalf in the meantime.