Answer:
In this context the verb meet means to see and talk to someone for the first time, which in spanish is conocer (to have a notion or idea of someone from the first impression).
In this sentence the verb is in past tense (met) and we have the time adverb yesterday.
So, the spanish verb conocer must be conjugated in past tense, taking into account the subject of the sentence yo (I):
Yo conocí
Therefore, the right answer is:
Yo conocí a Luisa ayer.