In Chapter 2 we find out that Lady Russell has twofold objection to Mrs. Clay: situation and character. The first objection seems snobbish, but the second is very reasonable. In defense of Lady Russell, one has to ask both what Elizabeth sees in Mrs. Clay, and what Mrs. Clay sees in Elizabeth.
In Chapter 3 we have the opportunity to judge ourselves when Mrs. Clay speaks. It seems obvious that she is trying to help her father, but she is also ingratiating herself to Elizabeth :
"You need not be afraid, Miss Elliot, of your own sweet flower-garden's being neglected"
and to Sir Walter with the following nonsense:
" In fact, as I have long been convinced, though every profession is necessary and honourable in its turn, it is only the lot of those who are not obliged to follow any, who can live in a regular way, in the country, choosing their own hours, following their own pursuits, and living on their own property, without the torment of trying for more; it is only their lot, I say, to hold the blessings of health and a good appearance to the utmost: I know no other set of men but what lose something of their personableness when they cease to be quite young."
And so, after Chapter 3 I thoroughly dislike Mrs. Clay. Is she clever? It seems anybody with sense would see the insincerity of such speeches. Does she know that, or she thinks she is cleverly subtle? I suspect that such flattery was not only socially acceptable, but normal.