Other than jade, there was a sapphire mine nearby as well, though not as big as the jade mines. It was impossible for jade and sapphire to appear in the same vein unless there were some special circumstances, but they were commonly found in the same valley or district.
The sapphire mines were closer to another small town about an hour away due to the rough and winding roads (though actually less than half the distance if one had a straight line path).
Since digging out her own mines was not possible, she should swipe a bit from the established mines. Anyway, these would be useless in 3 months! She's here to prevent waste!
As for why she didn't feel as guilty from stealing from these versus stealing from the shops was simply because the owners were big corporations and their corrupt government. Losing a few (hundred) stones wouldn't kill them. They might not even notice there was something missing in a month.
