Which preposition to use with spectatress

of Occurrences 3%

So stood Eliza on the wood-crown'd height, 270 O'er Minden's plain, spectatress of the sight, Sought with bold eye amid the bloody strife Her dearer self, the partner of her life; From hill to hill the rushing host pursued, And view'd his banner, or believed she view'd.

from Occurrences 1%

Of all the little incidents of the day, Dot was the amused and open-eyed spectatress from her chair in the cart; making a charming little portrait as she sat there, looking on.

Which preposition to use with  spectatress