En esta pregunta conjugaremos el verbo "ser" ó "estar" en Pretérito Imperfecto (Copretérito) : "era". La frase correcta es: "¿Quién era la señorita que vino ayer por la tarde?". Con el verbo "ser" ó "estar" conjugado en Pretérito Perfecto Simple sería: "¿Quién fué la señorita que vino ayer por la tarde?" y es correcta también. El Pretérito Imperfecto se usa para expresar una acción comun en el pasado. El Pretérito Perfecto Simple expresa acciones concluídas en el pasado que están separadas del presente en un período de tiempo ya terminado.

Well, you could use also the verb in the present tense as this (remember the open question mark in spanish): ¿Quién es la señorita que vino ayer por la tarde? I think this is the correct version of this sentence. Because the verb "ser o estar" is related with the existence of the "señorita" and she may be still alive, if she is allready death, then you should conjugate the verb in past tense. However, if you say: ¿Quién era la señorita que vino ayer por la tarde? It would be perfectly understood in spanish. Regards. Alí from Mexico (we speak spanish here)

hey this question is quite interesting in terms of habitudes of speakers!. I ll tell you my notion. "era" because you are talking about someone specific (gramatically determined/defined), i mean, a person, so it is suppossed that she still keeps being,,,,althought she is not here anymore. So, look at this examples: 1. quien ERA la señorita que vino? .....defined object (la señorita) 2. Quien FUE que vino?......................undefined object (que (?)) see the difference?

I think "fue" is correct, since "vino" is in the past, not the imperfect tense, so you are talking about a specific point in time, rather than a continued activity in the past. Of course, I am not fluent, so could be wrong :)