I encountered this curious sentence on page 234 of the 1859 novel, Natalie; or, A Gem Among the Sea-Weeds, by Emma V. Hallet writing under the pseudonym “Ferna Vale”, marked here in bold:
In a few words he informed her of what he had learned from Mrs. Santon the day previous, but what was his astonishment to find her totally ignorant of the circumstances, not hesitating to declare the whole a base falsehood.
“I had not a doubt of the falsity of the report,” said Delwood; “but what can have given rise to such a statement? Surely, your mother would not wish to injure my feelings, by repeating what may have originated, without foundation, among the servants, and she could not have herself credited!”
Winnie saw the truth at once, knowing as she did the character of her, whom, if she had ever looked upon as a mother, must from this moment forfeit every claim upon her feelings, unless it were that of utter contempt.
“Mr. Delwood,” said she, raising herself to her full height, her slender fingers clenched together, every nerve ’roused to action, — “if you would not insult me, never again call the woman who has had the heart to cast such a slur upon the character of her whom we know is innocent, my mother! It is not to injure your feelings that she has invented such a vile scheme, but it is by injuring Natalie’s character in your eyes, she may banish from her heart all future happiness. Nay, do not start at such a strange declaration from my lips; you are the only person, out of my father’s household, who has a suspicion that our happiness is not what it once was; but since it has come to this, I will, at the risk of disclosing to the world what it were wisdom to conceal, establish the innocent; and rest assure that what I say is true, — this has originated not amonth the servants, for there is not but would kneel and kiss the very ground upon which are dear Sea-flower treads.”
(The context is that Winnie’s new stepmother has proven to be an ill-natured woman.)
The whom seems to be correct (accusative case, I think: she had ever looked upon HER), but then the “must from this moment...” feels disjointed, not properly connected to the first part of the sentence.
Is this use of whom in fact correct? How would one analyse the complete sentence in question?