Let's look at the potential worst case scenarios here.
Ju-ae ascends to the leadership of North Korea well aware of the the precariousness of her position. Given that she's a second-in-line choice, and the first woman to take the reigns of the Kim dynasty, she has so much more to lose, and so much more to prove. So, with the assistance of her allies in the military, she commits to a nationwide cleansing of those she deems her enemies, resulting in a gross amount of unnecessary bloodshed, possibly leading to a small civil war as various factions in the government fight for their very survival. Once the dust has settled, she comes out the victor, and we're left with a battleworn hardass who will unite the country through renewed fervor against the west, the results of which will make us long for the days of her more reasonable predecessors.
The military, realizing they're the true power in North Korea, takes advantage of the situation to stage a successful coup that deposes the Kim dynasty entirely. The end results will be a more militant, and more competently run country that will likely align itself more closely with China.
The first scenario comes to pass, but the sides are more evenly matched. A prolonged civil war results, destabilizing the entire region as it spills over into China and South Korea. Eventually, China steps in to protect its own interests, likely annexing the country in the process. The rest of the world doesn't respond too well to this development, and tensions rise as a result.
The whole situation is rife with peril.