What does "tienes las pestañas largas o cortas? " mean

Do you have long or short eyelashes , that's the translation

It is telling you if you have short or long eyelashes

Pedro, josie, y heather fue a la quinceañera de virginia. the question is asking who went to the quinceañera. the person answering the question should answer using the ellos, ellas, and ustedes form if they were not part of that group of people.