Look for a 600 EFI. The exhaust valve was introduced in 2001. The 2002 to 2004 chassis is a superior choice. I had a 2004 570 MC for my wife. She now has a 2006 600 Crossfire with a 2 inch track and loves it.
The 500 will not have the horsepower she is used to with the 94 EXT.
The $1000 dollars is well worth it. That 600 has a 144x2 and is lighter. the 500 is a 136x1-1/2. The 600 will also get alot better gas milage. When I had my 500 I had to stop playing early casue I was running out of fuel. If you can afford it you will be alot happier with teh 600. I went from a 2001 500 to a 2004 600 and was very happy I did.
Maybe post the Prices you can get M5 or M6's really cheap.
We start riding at 7500ft in UT and a well tuned 600 with a 144 is near perfect for my old lady. some times she gets beer muscles and i think she needs more sled. A m6 with a 153 track and a pair of 10'' powder pros will make her feel like a pro. happy wife happy life.