pattern scaling

[banthetubetop.livejournal.com]

So, I made myself a shirt this week. I pretty much made up the pattern, and now my coworker wants me to make her one. I told her I would, though she's considerably smaller than I am. Does anyone have any ideas for scaling my pattern down? It's an empire-waisted tank top, and the bottom part is pretty much just made up to fit waist/hip measurements, but the top part is what I'm worried about.

Thanks :) I've been sewing like a fiend (this week I've made a shirt and 2 skirts, plus I've made 3 dresses and another shirt this summer) so I'll post pictures sometime soon because I'm actually pretty proud of how they've come out.