In addition to the advice above, here are my comnments:
The 24-70 is an awesome lens, however, it will not be wide enough on a crop body camera (7d, XT,etc). I suggest getting the 17-55 F2.8 which is the crop body equivilent. It also has image stabilization which the 24-70 lacks so shutter speed is one less thing you have to worry about (unless the subjects are moving).
The 70-200 is an awesome lens too, but on a crop body, I think it’s going to be too long a lens. Both these lenses are ideal focal lengths for a full frame camera. Since you are shooting outdoors in good light consider the 24-105L F4
The 50mm F1.8 is a sharp lens, but is useless for anything other than still portraits. It hunts in low light and focuses extremely slow. You will not capture all the action if you use this lens during anything dynamic.
The controls on a full frame are just about identical as that on a crop body as far as shooting modes. There is no difference, and one isn’t more difficult to use than the other. As LBPHOTOGRAPHY said, the full frame will allow you to shoot clean at a higher ISO to preserve natural light, however if you don’t know about techniques like “dragging the shutter” while using a speedlight, none of this will really matter. Sounds like you will have decent light too shooting outdoors during the day.
Ideally, you will have two bodies…in case of failure, and to have two different lenses on you. A macro lens is nice, but not required. The 17-55 is a decent, sharp, portrait lens as long as you shoot closer to the 55 end. A fast prime would be nice too….35, 50, 85,etc. Unless you have EF-S lenses (like your kit lens), they will fit both the crop body and the full frame. I wouldn’t use your kit lens for a wedding.
You will want to use fill flash, especially to overpower shadows on the face. The 430EX (I think the one you have??) is too slow for weddings. You have to press buttons to adjust the flash exposure compensation. The 580EX has a control wheel and it’s much faster. You will also want a battery pack for your flash.
Get a large memory card. They rarely fail, and changing them typically comes at the worst time. An 8 Gig would be good, and get a lot of them. If you rent a 5D MII you will only fit about 300 images on an 8 gig card so you will need at least 3.
Learn how to position people in the sun, you may want to bring an assistant and a large reflector for doing afternoon portraits.
Honestly, I am not trying to burst your bubble, but this doesn’t seem like something you are ready for. If she really has a budget of 2K she should be able to find someone with decent equipment that has experience shooting weddings. Definitely something to keep in mind if you don’t want to deal with the pressure. There also will be a big dent in the pot once all the necessary equipment is rented and purchased.
4 Day Rental Fee’s
7D – $140
17-55mm – $70
second lens – ~$70
Canon 580EX – $75 with battery pack
Decent high speed flash cards are going to cost at least $50 each.
So here you are at about 500 assuming 2-3 memory cards, and there is still stuff I am probably missing.