Well something super responsive is usually harder on the knees. You basically want the balance between responsive and forgiving. Forgiving enough that you don't have to muscle the board around, but responsive enough that your legs don't have to do ALL the work. Also some form of rocker is better on your knees. Bataleon is a maybe as they are easier to roll on edge and whatnot, but they do still require a bit more work than rockers. Fun as all hell though.
Bataleon Feelbetter 149, Nitro Pro Series Maas, the Cadence is a good option but whatever size is below the 151 is probably what I'd go for. At 155 I could ride the 154 Blacklist (chunky brother of the Cadence) everywhere from 6ft pow to street rails, Flow Jewel 149, or If you're into that waiting thing the Signal Vita is optioned with camrock for '13 and I haven't put a girl on one that didn't love it. So a 47 in that.
Also a not, get bindings with some form of canting and good dampening, we can help with that if you like, and for sure get some properly fitted boots and some after market insoles. I don't know if Remind makes a womens size but if they do, check them. One of the best if not the best after market insole for snowboarding.
Go ahead, drink that kool-aid.
FS: Forum Sauce 142 $200 plus shipping
FS: Flux SE30 $75 plus shipping