"Yesterday there was a different girl here."
Translation:Včera tady bylo jiné děvče.
This is a major disadvantage of Duolingo. While such a sentence is technically correct, I cannot imagine anybody using this word order. It always seems to be '....tady byla..'. The 'Byla tady..' would be used in question.
This as well as above comment, it is understandable but the syntax just is not natural for a czech.
"Tady byla jiná holka včera" is no good either, I see. Is it a word order thing again? I think I have to stop putting včera at the end... that seems to always be my mistake.
You should stop putting it there unless you have a strong specific reason.
Your sentence is grammatically possible, but strange. It corresponds to "A different girl was here YESTERDAY." (and not on Friday as you suggested before...).