AEM makes the best cold air intake for her car... it runs about 200 shipped on ebay. www.aempower.com

Exhaust = About 10 HP = $600
Intake = About 10 HP = $200
Headers = About 5 HP = $250

Lowering and Rims are definitely the best mod for looks... But also the most expensive...

A good set of rims will cost about $1000. And a good lowering professionally installed will be about $600, you have to buy the springs and the shocks... and a camber kit is best as well.

Also, for looks, check out clear corners, bumper lights, etc. She might like how altezzas look also.