Well, someone should :). She has been roundly abused recently. And since she is my favorite character ...

I suspect the initial hostility directed at LS derives from ED's inner thoughts in Ch.22 ("Lucy was naturally clever ..."). But these remarks are merely Elinor's opinion, and I find them a mystery because they are offered so early, before LS has done much of anything. Since they are ED's thoughts, and not the narrator's opinion, much less JA's considered judgement, we should not accept them without reservation.

At this point, early in chapter 22, the character assault seems strangely unwarranted. LS has shown a tendency to butter up Lady Middleton by playing to her children. Lucy's sister has shown curiosity over Elinor's doings in Norland. But Lucy has not. And asks her sister not to continue the intrusive questioning. And unless you believe that LS has goaded her sister into this line of inquiry (and where is the evidence of this?), and therefore capable of any evil, you cannot accuse LS straight off of being a snoop and a conniver.

Elinor may resent the necesssity of spending several hours daily with two women she considers dull and tedious, but that is Sir John's fault, not Lucy's.

So, why the character assault at such an early stage ("she was ignorant and illiterate")? I suspect that because ED feels she cannot compete in the looks department with Lucy, she must chop her down to size by noting her lack of education and good grammar. Her criticism can be seen as envy.