Native Spanish speakers often drop the "s" at the end of a word. This has been explained on other threads, but not in the Duolingo lessons. I guess they are preparing us for what we will encounter in real life. This sentence is particularly confusing because nothing else in the sentence gives away the fact that the pronoun is referring to something plural.
check your native language, we drop sounds all the time. this was a reading exercise for me so it's ok, if it was an listening exercise i'd complain, because listening to this sentence there's no way to tell. But that's what would happen in real conversation in spanish, you'd know not from what they said, but from the context.
This is a sentence with Direct Object and always it uses transitive verbs. This personal pronoun-ella- and the verb -necesitar- make the action over the O.D. "Los" replace a person, an object. Example: She has dogs, chocolates or friends then "she doesn't need them (them=dog, chocolates, friends) for any reason". In Spanish "ella no "los" necesita.(¿a qué/quién no necesita?: a ellos, a los perros, a los chocolates, a los amigos). The "object pronoun los" is placed before conjugated verb. Hope this helps . Saludos