From the article:
She also mentioned that South Korea should strengthen its ties with the United States to guarantee protection under its “nuclear umbrella.”
I suspect that there is a lot more to this statement than meets the eye. It's basically a warning to Obama that ...
either he makes an explicit statement to this effect,
or South Korea will create their own nuclear umbrella.
Or, much more likely, they will reveal that they've had nukes for a while now -- with our knowledge and tacit approval.