Right now, she is leading all the potential GOP candidates, by a very large margin.

http://www.realclearpolitics.com/epolls/2016/president/us/general_election_christie_vs_clinton-3766.html

Christie vs. Clinton (Hillary: +9)
Huckabee vs. Clinton (Hillary: +12.4)
Paul vs. Clinton (Hillary: +9.4)
Bush vs. Clinton (Hillary: +10.
Ryan vs. Clinton (Hillary: +9.3)
Cruz vs. Clinton (Hillary: +14.0)

So, it is almost certain.