I should have added this here...
Jean accepting that she acted as “a vessel for death” doesn’t negate the fact that, in the end, it was a clone imbued with a fragment of her psyche, using an exact copy of her “brainwaves,” but thrust into situations that involved mind control and falsified “realities” and memories - situations Jean had never been subjected to - that was responsible for the “sins” of Dark Phoenix. It’s also important to note: We’ve seen how another Jean clone imbued with and animated by the same exact fragment, and also subjected to mind-control and falsified memories, would eventually act.
In the past, Jean has taken responsibility and faulted herself for the actions of both Dark Phoenix and Madelyne Pryor. Being the empath that she is, coupled with the fact that both clones were literally made “from her,” it’s understandable why she feels this way. On some level, she will always blame herself for the actions of Dark Phoenix. In part, this is why I love her: She isn’t afraid to acknowledge when she has been a part of or done something wrong. Note, however, that she does not refute what T’Challa says here. She only makes clear that a part of her was connected to Dark Phoenix, i.e., “a part of it,” which, of course, is true. I take her admissions during the speech to mean the same thing.