I got marked off for not using "in", i.e., "Neha is speaking English."

I know the original has में, but I honestly feel like there's no real difference between the two, so I suggested it.

Yep, I had the same thing as AnUnicorn. IMO both versions are correct and actually without the "in" is probably more common.

I think अँग्रेज़ी should be written as अंग्रेज़ी.

Edit: After doing some research, I found out that अँ is might actually be more correct than अं in this case, but nowadays many people online replace chandrabindu ँ with anusvar ं.