On the off chance that no one has answered you yet, she and her "husband" are the last of the presidential couples to get SS protection forever (or as long as they live--no comment here).
Starting with President Bush, SS protection extends only for 10 years.
Yes. So is Chelsea. Bubba-1 gave them SS protection for a additional 6 months when he left office,and Bubba-2 extended it. I'm not sure when it ends for either. Or even if it will end.