Hilary did not march on Benghazi with the terrorists on September 11th of 2012. She didn't carry an AK-47 or pull the pin on any grenade. She was half a world away, but the attack's success was a direct result of her poor decisions. The U.S. intelligence community caught wind of a possible attack months before. Separately, the head of security at the embassy requested additional manpower from Clinton's State Department, but was turned down. With this combined knowledge, Clinton did nothing, leaving the embassy vulnerable when she could have beefed up security to make it an unattractive target.
Hilary Clinton had prior knowledge of the lack of security at the compound and had nothing done about it. It was her job as Secretary of State to ensure the proper security was in place to prevent these kind of attacks from happening. She then knew she was at fault for the Benghazi attack, but still chose to lie about her part and pushed the blame onto others.
Yes, Hillary Clinton holds some responsibility for the Benghazi attack. Starting with the removal of Gaddafi, the events leading up to Benghazi and the decisions that were made created a severe destabilization within that country and its region. Ambassador Stevens also reportedly asked for additional security because of escalations in the area, but his request was denied just prior to the embassy attack.
Hillary Clinton is responsible for the Benghazi attack. She was not awake for the 3 A.M. phone call. She had but pressure on the Ambassador to be their so they can set up the embassy and it would be the crowning jewel of the Clinton State Department. She was not awake when they needed her.