I've always wonder what would of happened if the hellfire club hadn't mess with the phoenix and what direction they would of taken Phoenix to next.  But with continual comics and different writers popping up every few years, it gets convoluted.  If they are the same we can say that the Phoenix is the destruction part and Jean is the part that saves.

No, the Phoenix Force couldn't handle the human emotions, so it went crazy, even in Endsong, it didn't even know the emotion of love, in a way Jean didn't do it because she was in the cocoon, but the force did, after she returned and was made one with the force, still it wasn't her, but she has the memories of the Force doing so though.

The Phoenix Force copied Jean's body and took a piece of her psyche when she first encountered Jean...The force had the body, memories and personality of Jean but it wasn't truly Jean...The piece of Jean that the Forcde took faught with it during the Dark Phoenix saga which explains a couple of her bipolar moments...After the Force commited suicide the real Jean was found however she didn't lose her connection to the Phoenix...Jean's whole being is favored by the Phoenix hence why she didn't lose this connection...But in order to become one with this force Jean had to understand the balance of life and death which is why she died and ressurected so many times...After learning she has now become one with the Force as WPOTC...So no it Dark Phoenix wasn't her fault....

this ^