Find this line in lib, and remove ucwords.
$col["title"] = ucwords(str_replace("_"," ",$c));

You can also define each column title. see demo example-full.php

in which file under lib folder should i make this replacement?
it would have been great if this was a settable parameter
My field names are case sensitive

Hello

You can loop through column names (as done in emailed example) and set title for column without ucwords.

Changing core lib is last thing todo.