whoa boy... i could go on and on about the lack of selection in women's bike clothing... but i won't
well... first i think it's awesome when i hear guys say they want to buy stuff for wives/girlfriends to encourage them to keep riding... but i also suggest just taking her shopping and letting her pick out stuff... not only do you need to worry about general sizing and design preferences... but you also have to take into account the difference in sizing with (and i'll just be blunt) boobs, hips, butt, thighs... so i'll chime in with what i like, but take it with a grain of salt since i might not be the same body type as mrs. sk1er18.
for reference, i have a very straight body type (not much difference in the chest, waist, hip ratio)... 5'4", 122 lbs area. in "real" clothes, i'm usually a small, or size 4 dress size
shirts: i own a variety of jerseys: primal wear, v-gear (custom jersey), louis garneau (not sure i spelled that right), giro, novara (REI brand)... and they're all size small but some are a little baggier than others even within the same brand. i'm not usually a big jersey wearer tho. i prefer just general athletic tops (which i'll talk about in a minute).
shorts: i only wear fox baggies... size small. i've tried other stuff but none have really fit that straighter body type i was talking about earlier. i usually have the problem with the waist being too tight with the butt/hips/thigh area being gigantic. (Pearl Izumi runs small... Zoic & Giant have run big... Canari more or less true to size)
jackets: i have novara, suguoi, harlot bike wear (but they're clothing up shop so all sales are final) and again all size smalls. to be honest, i think i have an easier, more forgiving time buying clothes since i don't have to worry about big boobs.
non-bike stuff... i run and sometimes kickbox too... so i like to look for multi-purpose clothing. i love Athleta and GapFit clothing. even if it's meant for running, i can usually wear them for biking too... they're pretty good with making shirts a little longer to cover any potential crack moments... i fluctuate between XS and S. Athleta have this magic material that somehow doesn't smell. it's weird and awesome at the same time.
as for bike shops that carry women's clothing... um... well... in my experience, it's usually a pretty crappy selection usually with only one or two brands in limited sizing... you might have to hit up a variety of stores or check out stuff online (and really look for reviews... women are not shy about what they like and don't like in their athletic clothing)
sorry this is kinda long winded... i hope some other ladies chime in because i know everyone has their own preferences and there's a lot of different body types out there....