hi there, why is it 'bylo' and not 'byla' as the sentence is about a girl?
Word "děvče" is grammatically neuter, not feminine. It is similar to "das Mädchen" in German which is also neuter.
Words in Czech can have unpredictable grammatical genders, you have to memorize them.
"there was a different girl yesterday here" is not possible?
It would be "There was a different girl here yesterday." Unfortunately, though, I don't understand English well enough to articulate why that word order is required.