Megan, do you know what model it is exactly? Then I could at least tell you how much a replacement would cost...
Secondly, re the sand — there are http://www.amazon.com/Beseler-DustGun-Compressed-OZ-227gm/dp/B00009R69C (products) available that might be worth a try, before writing the camera off altogether (particularly if she knows someone 'handy' enough to dare open the outer casing). Dust, sand etc. used to be pretty much instant death to any electronic device with lots of small, precision moving parts — in traditional film cameras, these would be things like the film advancement mechanism, the shutter, the lens focussing barrel, etc. Digital cameras don't have quite as many of these sensitive areas, but they do still have some (especially if it has a zoom lens that bzzz's out into position when the thing is turned on). What they do have, though, is loads of circuitry and electrical contacts that might are very vulnerable to salt. In fact, that might very well be the problem, rather than the sand.
Tbh, I suspect that the Sony repair guys may be quoting a prohibitive price for the repair in the hope that she/you'll 'go away and buy another', because it's just not worth their (expensive) time trying to track down and eliminate the fault — which could be down to any number of other factors. Once they've found any trace of sand, that's enough to invalidate the warranty on grounds of improper use/negligence, so it's no longer their problem.
In sum, I'd be inclined to have her let a 'techie' friend open it up with a precision screwdriver and try a little bit of air-blasting — with no guarantees, of course! — and then resign herself to buying a new one. They're getting cheaper by the day...