Thanks for clarifying Anne-Marie I agree Mrs. Bennet views Mr. Collins as a less desirable catch than Bingley both as a man and of course as to fortune. However, she does think well of him. She “seriously commended Mr. Collins for having spoken so sensibly, and observed… that he was a remarkably clever, good kind of young man” (Ch. 18).

I suspect Mrs. Bennet feels if a man is respectable and a gentleman he is acceptable and ought to make any of her daughters happy. She does not appear to connect spousal compatibility to domestic felicity for it does not seem she recognizes how it is a problem in her own marriage. I am not convinced it would ever occur to her that Lizzy would not be happy with Mr. Collins. After all she is startled when Lizzy rejects him and lays the fault in her being a “very headstrong, foolish girl” who “does not know her own interest” (Ch. 20).

Of having another daughter married to Mr. Collins, she thought with equal certainty, and with considerable, though not equal, pleasure. Elizabeth was the least dear to her of all her children; and though the man and the match were quite good enough for her, the worth of each was eclipsed by Mr. Bingley and Netherfield. (Ch. 18)

I think Mrs. Bennet’s conclusion Mr. Collins is good enough for Lizzy is based not only on his “assets” but on how she rates Lizzy’s value on the marriage market. In Ch. 1 she says “Lizzy is not a bit better than the others; and I am sure she is not half so handsome as Jane, nor half so good-humoured as Lydia” which suggests she feels beauty and good humor are the ultimate charms to attract a husband. Jane is a great beauty with a sweet disposition therefore she has more value than her sisters and expects her to secure not just a good match but a great one—she is too good for Mr. Collins. Lizzy is not as handsome as Jane or as good-humored as Lydia so Mr. Collins is good enough for her and her mother might believe she has little hope of doing any better. I think Lizzy is Mrs. Bennet’s least favorite child because she does not understand or value her “quickness” (unlike her husband) and in fact her scolding of Lizzy in Ch. 9 may show that she considers it a less desirable characteristic for attracting husbands:

"Lizzy," cried her mother, "remember where you are, and do not run on in the wild manner that you are suffered to do at home." (Ch. 9)