The $130 you paid was about the most I personally would have paid for that tablet. So, don't feel like you stole it from her

I've seen them go lower than that (yes, for new in box).
I hesitate to ask, but why were you concerned about replacing yours with an identical model, when there was nothing wrong with yours?
As for price, you can probably sell it between $79 to $99 assuming no scratches on screen. I wouldn't sell it, why not have 2? For $20 you can easily put n2aOS on one of them and have yourself a nice KitKat tablet. (actually that $20 would license both of them, but I am certain you want to keep one of them stock).