It is sad but Lady Elliot’s anxiety to instill “good principles and instruction” (1) to her daughters may have been fueled because she saw the influence of their “conceited, silly father” (1) on her eldest. Sir Walter’s influence on Elizabeth began early:

She had, while a very young girl, as soon as she had known him to be, in the event of her having no brother, the future baronet, meant to marry him, and her father had always meant that she should. (1)

I think Elizabeth’s adopting her father’s choice for her rather than dreaming up her very own prince charming illustrates his early influence. Another hint of Sir Walter’s influence might be in Elizabeth’s previous feelings about the Baronetage:

Then might she again take up the book of books with as much enjoyment as in her early youth, but now she liked it not. (1)

The description of early youth suggests to me the teen years. I think by the time Lady Elliot passed away Elizabeth and Sir Walter were pretty much simpatico:

Elizabeth had succeeded at sixteen to all that was possible of her mother's rights and consequence; and being very handsome, and very like himself, her influence had always been great, and they had gone on together most happily. (1)