It is true that the phrase "a ella" is more specific than "le", but in Spanish, if you leave out the "le" it just doesn't sound right to a native speaker.

Long explanation: Defining the terms: We should explain some terms you might see ... Popular Phrase: sound right | Spanish Adjectives

For this to sound right in English we would have to say, "The teacher wants us to study." The problem is that in Spanish there is only one pattern used for "influence ...

It wouldn't sound correct in English to insert the word "that" in this sentence, but in Spanish it doesn't sound right to people who are native speakers of the language ...