You can't just say "Ella no gusta comer en los restaurantes" or " Todos gusta la comida china". However, you could say "Ella no gusta de comer en los restaurantes" or "Todos gustan de la comida china" (adding the preposition 'de'). When you say "A ella no le gusta comer en los restaurantes. A todos les gusta la comida china", the verb "gusta" does not literally translate to "likes" as the subjects are different than what they would be in English. So even though it seems like the subjects in these sentences are "ella" and "todos", they are actually "los restaurantes", and "la comida china" "A todos les gusta la comida china" does not directly translate into "Everyone likes Chinese food". It would translate to something like "Chinese food is pleasing to everyone". In this case, the "TO" in English translates to the "A" in Spanish, which is a necessary preposition.