Take this sentence:
You saw her knit a scarf.
La viste tejer una bufanda.
Le viste tejer una bufanda.
I'd say that both are correct, since the direct object of "saw" can be understood to be either "her" or "the action of knitting a scarf". However "la" sounds better.
Now put that into a subordinate clause:
Grab the scarf that you saw her knit.
Agarra la bufanda que la viste tejer.
Agarra la bufanda que le viste tejer.
Now I'd say that "le" is the way to go, to the point that using "la" feels wrong. Even when technically the role of each element in the sentence is the same.
Why is that? Are both correct? Am I guilty of laísmo in the first example? Am I not identifying the direct and indirect objects correctly?
So far I've got 2 answers (one deleted) saying that it is laísmo and "le" should be used, and another two answers stating that it is not and "la" is correct. So which is it?
I'd like to expand in the above examples, in a quest to get more complete answers.
Fact 1: we can take "her" out of the sentence and the meaning would be more or less the same:
Viste tejer una bufanda. Agarra la bufanda que viste tejer.
Here, it is pretty clear that "tejer una bufanda" is the DO in the first sentence. So the question would be if introducing "la" shifts the DO to "her", whoever she is.
Fact 2: a common way of telling the DO from the IO is by switching to passive mode. And then we have that:
Viste tejer una bufanda
-> Tejer una bufanda fue visto por ti.
La viste tejer una bufanda
-> ?? Ella tejer una bufanda fue visto por ti (DO = ella) ??
-> ?? Tejer una bufanda por ella fue visto por ti (DO = tejer) ??
I'm not really sure how that should be transformed.
Fact 3: if we switch to passive mode only the "tejer" part, then "she" can no longer be the DO, not even the IO:
La viste una bufanda ser tejida
Le viste una bufanda ser tejida
Viste a ella una bufanda ser tejida
Viste una bufanda ser tejida por ella
So far the only thing I'm getting out of this, is that ella cannot be the indirect object. She must be either the direct object, or some kind of "authorship complement", if such a thing exists.
Would that mean that it is the use of "le" that is wrong?