The reason she's so heavy is found everywhere: the frame, the engine, the wheels, the exhaust, the tank, the bodywork. You can't really change the engine or frame without serious surgery, so unless you do this sort of thing yourself for kicks, that's out. To lose any serious weight, you'd have to replace all of the others: the wheels, tank, bodywork, and exhaust. When all that is said and done, you'd have spent upwards of 5 large, and you would reduce the weight by maybe 30-40 lbs - that's well over $100 per pound!!! That's why:
1) If you really want a lighter bike, buy a different bike from the start - it's WAAAY cheaper to have the manufacturer do this than you.
2) It is far cheaper to lose 10lbs from your person than from your bike, thus the advice about losing weight - he's not kidding.
3) But if you've got the time, money, and inclination, yes you can lighten the old girl if you really want.