Citing an intelligence official in the United States, the JoongAng Daily said that Kim had surgery for a brain tumor in 2013 in Paris.
© Photo: "Vesti.Ru"
After the surgery, she lost a lot of weight, dropping to 35 kilograms, the official said.
North Korea's state media announced Jang's execution last month, labeling him a "traitor for all ages."
© Photo: "Vesti.Ru"
Her fate has been the focus of attention of North Korea watchers since Jang's execution.
The younger sister of Kim Jong Un's father, the late leader Kim Jong Il, she was seen last month in a Korean Central Television film purported to praise the current leader's achievements.
© Photo: "Vesti.Ru"
She appeared in a scene believed to have been filmed when Kim Jong Un visited, in December 2012, the Kumsusan Palace of the Sun, where the leader's grandfather Kim Il Sung, the founder of North Korea, and others are laid to rest.
Jang is known to have accompanied Kim Jong Un on the visit but the footage was edited not to show his image.

Determining whether stories about North Korea are true or false means delving into a very wide, grey area where the genuinely surreal mixes confusingly with the patently absurd.
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For example, which of these reports about leader Kim Jong-Un appears - at least on paper - the more likely?
That he executed his uncle by feeding him naked to a pack of starving dogs, or that his birthday celebrations in Pyongyang were led by a serenade from a former cross-dressing, NBA all-star with a penchant for facial piercings and celebrity wrestling?
The latter is borne out by a YouTube video showing ex-Chicago Bulls guard Dennis Rodman's off-tune rendition of "Happy Birthday" before an exhibition basketball match watched by Kim on Wednesday.
On the other hand, the death-by-dog story, which was picked up by some international media, was apparently based on a satirical tweet posted on a Chinese website.
This was then picked up by Chinese newspaper Wen Wei Po, leading to shocked headlines in the Western media.
Differentiating fact from fiction is particularly difficult when it comes to North Korea given the country's profound isolation, which makes any story not sanctioned by its highly secretive regime almost impossible to verify.
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At the same time, international interest in what goes on in North Korea is enormous, especially when it comes to sensational stories that satisfy a widespread perception of the country as brutal, backward and bizarre.
These factors combine to create a cavernous media echo chamber that provides resonance and substance to rumour and speculation.
Elements can then be cherry-picked and put together into a sensational news item, as happened with the rumours swirling around Kim's purge and execution of his uncle and political mentor Jang Song-Thaek last month.
The most spectacular version would read something like this:
Kim Jong-Un had his elderly uncle, who had an affair with Kim's wife, fed naked to a pack of 120 starving dogs, thereby inducing a heart attack in his aunt who now lies in a vegetative coma.
A number of these elements originated from the mainstream South Korean media and North Korean defector-run websites - both of which, analysts note, have a vested interest in painting the North and its leadership as a source of unimaginable horror.
'A weird, wild place'