It's an interesting idea, but I never got that impression. I always thought Lady C wanted Lizzy and Maria to stay on at Hunsford, because she really pitied them for having to leave her glorious society behind. After all, what company at Longbourn could compare to that at Rosings? I do, however, think she is intelligent enough to prefer Lizzy's society to Mr. Collins's--but I think she would have preferred others' society to Lizzy's as well.