Mbender, are you separating her to feed her? I have to separate my three or the oldster won't get enough of his, and will get far too much of the TB's!
They get 'communal' hay, but put out in different piles. My rule of thumb is one more pile of hay than there are horses. Keeps them from guarding one big pile and not letting the others eat.
Yes, the measurement should be on the scoop somewhere.
I don't have any pictures of Mack, but he's about 14.2 h and around 950 lbs. He's got plenty of meat on those old bones.