Consider that she left office before Rouhani came in. She was not particularly eager to start any negotiations, that was Obama's decision and when he first wanted to test whether Oman could host secret talks he sent Senator Kerry to sound it out, not HRC.

Both Obama and Kerry thanked a long list of people involved when they spoke after a deal was reached. Neither included HRC, which given her position would have been unlikely had she played the critical role.

The multilateral talks were started long before Obama became President, but they did not include the US. The US JOINED those talks, after bilateral secret talks in 2013. Some of the early secret talks were when HRC was SoS and involved Jake Sullivan and William Burns who for the earliest part of that reported to her.

However, Wendy Sherman and Kerry, personally, negotiated the interim deal, the framework, and the final deal. Kerry spent months working with his peers. After the interim deal, HRC was rather neutral on what they achieved and was not optimistic about success.

If you followed this, the foreign policy press was absolutely skeptical over the 2 years and spoke of it being a waste of Kerry's time. Even calling him delusional. When it was possible to be a failure, it was all Kerry's.