in a similar situation, just started taking my girlfriend backpacking. thankfully, she loves it after one fairly rugged trip.
my solution for our next trip was to get hiking umbrellas (these: http://www.amazon.com/gp/product/B001OPO7L8/ref=oh_details_o02_s00_i00?ie=UTF8&psc=1) and wild things gear is having a sale, so i also got her a wild things gear hooded windshirt for ~$35 (not the lightest solution, but cheap and versatile, with a dwr coating)
and then i got some driducks for cheap, light backup. (~$20 and ~10oz for both jacket and pants)
my plan of attack (should it rain) is to be able to use the umbrellas and windshirt to show her it's possible to be just as, if not more comfortable without full waterproof gear, but then have the driducks as backup just in case.
i also grabbed the zpacks pillow dry bag ( http://www.zpacks.com/accessories/dry_bags.shtml ) and the driducks will serve double duty as stuffing for pillows.
i also got her a set of the insulight jacket and pants from wild things gear (mostly because i can't resist a good deal, and they were on a tremendous sale). also, not the lightest, but she tends to get cold easily, and the jacket (with epic fabric/primaloft insulation), is still lighter, more water-resistant, and more insulating than the rei softshell she would insist on bringing otherwise.
with the epic/primaloft pieces she'll have something she can throw on quickly to warm up with when stopped if we end up getting fairly wet in our water-resistant windshells.
i wasn't aware of luke's gear, looks nice and reasonably priced. something i'll definitely consider down the road. thanks for bringing it to my attention. (if money was no object, i'd definitely be ordering some of those pieces right now)