..mmm...seems a strange question to ask if you don't mind me saying so....even if the Kobo could display and control two books it would be uncomfortable to both be reading from a 6" screen....interesting though....at the risk of being faceceous, being so close to my OH would tend to make my mind wander from the plot.....
Why not just enter into the spirit of Christmas and buy her one of her own...or one for yourself if the one you have is hers...