You might be able to get away with just two jackets though, if you mix-and-match. I've done that on business trips. For example:
Day 1: black jacket with black pants
Day 2: white jacket with black pants
Day 3: black jacket with grey pants or a skirt
Day 4: white jacket over camel pants or sheath dress
This is just an example... and you'd need a different blouse every day. Red or black pumps would probably go with all 4 days worth of outfits.
With this idea, you just pack two jackets, three bottoms, 4 blouses, one pair pumps.
Since you're meeting with congress, I would err on the side of conservative, and go with a traditional, basic pump with no toes showing. Unfortunately, if you wear only pants, you will not be able to swap out flat shoes when you are walking (your pants will drag on the street). Skirts and sheath dresses would solve that dilemma. But that means all new clothes for this trip, since you don't own any!
Ann Taylor is a must, but do also check out Banana Republic and the petite section of your department store. Actually, check the suit section - often the petite suits are in that section, on a rack or two that says "petites." You may also want to hit Marshall's or TJ Maxx or discount places like that.
If you are going to be calling on Congress often, and you have need to invest in good quality suits and this isn't a one-time thing, then you may want to try Jcrew and the Theory line. Their suits are more expensive, but from what I hear, are well worth it.
If you are looking for an investment, a three piece suit would be a good idea - matching jacket, pants, skirts, or even a sheath dress (making it a 4 piece suit), all in the same fabric. Just make sure all the pieces fit and flatter you - they aren't worth it if they don't. And you will still need another jacket to mix and match for this trip though.
