It depends on whether the cause for this is temporary or not and on whether or not the Electoral College has already met and formally appointed her in its December meeting. If a President-elect for instance passes away after being formally appointed by the Electoral College in December but before being sworn in in January, the Vice-President will be sworn in as President.
In case of a permanent incapacity before the December meeting but after the election, things become complicated, all the more so since State Electors from some States sometimes are only authorized to vote for the incapacitated candidate him-/herself and not for any substitute. Also, there is no legal precedent here; President-elects so far only died (if they did) after being sworn in.
In all probability, the Speakers of the Houses of Congress would then temporarily assume the tasks of the Presidency while things were being sorted out.
Hillary Clinton?
Hillary Clinton has never been elected president. She apparently won the popular vote in the recent 2016 presidential election.
Hillary Clinton, the wife of former US President Bill Clinton, was elected to the Senate. She served as a senator from New York from 2001 to 2009.
Bill Clinton can not legally serve as Vice-president because he can not again be president, having already served two full terms. If Hillary were elected and died, the legally installed vice-president would succeed her.
hillary Clinton
So that she can get elected.
Hillary Clinton appears to have the lead at the moment, but the situation could change rapidly.
Assuming Hillary Clinton runs and wins in the 2020 election, she would be 73 when elected, older than Reagan who was 69. Hillary Clinton would be older.
Actually, she was not elected. She was "appointed"-- chosen by the president to be in his cabinet. (President choose the people they want for their cabinet, and then the senate has to confirm them.) Mrs. Clinton was chosen to be Secretary of State during President Obama's first term.
No. She was President Obama's Secretary of State for his first term. The recently reelected Vice-President is Joe Biden.
Hillary Clinton appears to have the lead at the moment, but the situation could change rapidly.
Hillary Rodham Clinton was elected to the U.S. Senate in 2000.