Snowboard Size for Beginner Woman

Good choice! Welcome to a new addiction! Later on when you start bombing down mtn. you'll want a longer board. I'm 5'0 and I ride a 146, I had a 139 at one point ;)

My friend about same weight and height, started with a 142cm and complained that it's not stable enough at higher speeds.  She tried my 150cm board and loved how she was grounded over bumps/moguls.  Now she's planning to get a 140cm since it's more flexible and easier to butter with.  Longer board = stable; shorter board = playful.  Hope this helps.

Thanks for the thorough response! That was extremely helpful. I have been looking at the Capita Saturnia and the Capita Space Metal Fantasy FK. Are you familiar with either of these boards? If so, which would you recommend?

With your weight n height, u are in the 138 range. I'll suggest a 140.
Since you're a beginner and I'm assuming that you won't be bombing down the slope too often yet, a longer board will be counter-productive mostly due to the extra weight and length which you will fatigue faster, more effort to control and manipulate, and less forgiving.
By the time you are bombing down slopes, you will have already learned how to control your board so a 140 won't be a problem. Plus you're a light weight rider, not having enough pressure on the edges will make the ride more sketchy. A longer board will have less pressure on the edges due to pressure disturbution.
If you're serious bout the sport, get a camber. It'll teach you more and help u progress faster.
If you just wanna have fun and only going to the slopes few times a year, it doesn't really matter which camber profile.
But try to stay away from stiffer boards, is easier to manipulate a softer board...or more forgiving.

of course this depends on the specific board design you're looking to get. but I'd reccomend the 143 as it will be longer as you progress a little.