Yuo, I think about 1150 should be right for her.
Another thing you could do, for both, the pony and her.
Get the slow feeder hay nets. Put their hay in there and they will slow down and eventually eat what they need. Works like a charm
Mine are down from 25lbs of hay a day to 15!.......no more wolfing down feed, they eat a little at a time and take a lot of breaks in between.