I certainly did not owe the suggestion of one incident
A long critical history has sprung up around this statement. Now that all
the extant manuscripts for the novel have been published in facsimile, it
would appear, at least from the written evidence, that Mary Shelley's
defence of her own artistry is accurate. Her husband read the manuscript
with careful attention, here and there suggesting variations in phrasing
that Mary Shelley incorporated into the final form of the novel. As the
editor of the facsimile edition concludes, "A reading of the evidence in
these Frankenstein Notebooks should make clear that PBS's
contributions to Frankenstein were no more than what most
publishers' editors have provided new (or old) authors or, in fact, what
colleagues have provided to each other after reading each other's works in
progress." For the full statement, see Charles E. Robinson, ed. The
Frankenstein Notebooks: A Facsimile Edition (New York and London:
Garland Publishing, 1996), I, lxvii-lxx.