In 2007, she opposed raising the cap. The WaPo describes her conversation with an Iowa voter at the time as follows:

"She told him she didn't want to put an additional tax burden on the middle class but would consider a 'gap,' with no Social Security taxes on income from $97,500 to around $200,000. Anything above that could be taxed."

http://www.washingtonpost.com/wp-dyn/content/article/2007/10/11/AR2007101101292.html

She criticized Obama in 2008 for proposing raising the cap, accusing him of supporting "a trillion-dollar tax increase on America's working families":

http://usatoday30.usatoday.com/news/topstories/2008-01-16-1797040513_x.htm

Then, last October, she said:

"And I want to look at raising the cap. I think that’s something we should look at how we do it, because I don’t want it to be an extra burden on middle-class families and in some parts of the country, there’s a different level of income that defines middle class."

http://www.alternet.org/news-amp-politics/say-it-aint-so-hillary-clinton-youre-open-idea-raising-retirement-age

This February, she said:

“Obviously, lifting the cap at some point or another is a very live possibility,” she said during a Des Moines Register editorial board meeting last month."

http://www.usatoday.com/story/news/politics/elections/2016/02/09/hillary-clinton-bernie-sanders-differ-details-social-security-plans/80078816/

But now she won't commit to it. As the New York Times points out:

"Her loud praise of Social Security doesn’t change the fact that she won’t commit to raising the cap on the amount of earnings subject to Social Security payroll tax beyond the current $118,500."

http://takingnote.blogs.nytimes.com/2016/04/15/clinton-and-sanders-show-their-exhaustion/?_r=0

Again, she stakes out positions on all sides of an issue. The question becomes, are we talking about the October 2007 Hillary, the January 2008 Hillary, the August 2015 Hillary, the February 2016 Hillary, or the April 2016 Hillary?

This is the pattern with her, on issue after issue. There's no way to know where she stands on anything, because her position could change next week.