YESS Im here!!!, here is what you should upgrade from your lists, now or later doesnt matter, only a matter of preference
1. Front and Rear Brake, change to Avid Juicy 3 (if you can find one) or Juicy 5 or Avid Ball Bearing 7
2. Shifter pods to a 9 speed, Deore (cheapest), LX - XT (Mid range), XTR (if you have a lot of money
)
3. Casette and chain (must if you are upgrading your shifter pods to 9 Speed)
4. Front and rear hub (Avid's only accept 6 bolt style rotor, unless you can fit your Avid calipers onto a Shimano rotor)
5. Make sure your gf seatpost length is enough for her (unlike mine)
6. Ask her if her saddle is comfortable, if not change it.
Kay now the explanation part:
1. I strongly suggest upgrading your brakes first because people say Sole is the weakest hydraulic break, Avid is one of the best in the market. Sole is a single piston, Avid's are two piston, two is better then one, better breaking power, modulation and etc etc. You get the deal.
2. More number of casette = easier to cycle because there are a extra lower gear ratio which makes climbing steep mountain easier
3. You must upgrade your chain, casette and shifter pods to be able to use 9 speed gearing, your Deore accepts 9 speed, chain upgrade to 9 speed or add a extra link, casette so you have a extra lower gear, shifter pods so you can shift to that lower gear.
Pretty confusing but you get the point
, I wont mind explaining again which part you dont understand