GR translation: But they pranced the screen full of the Sagittarian fire

[Mike Jing]

V482.29-483.2, P490.33-491.5   In Weisse Sandwüste von Neumexiko she played
a cowgirl. First thing, they’d asked, “Can you ride?” “Of course,” she’d
answered. Never been closer than roadside ditches in time of war to any
horse in her life, but she needed the work. When the moment came to saddle
up, it never occurred to her to be afraid of the beast pressing up between
her thighs. It was an American horse named Snake. Trained or not, it could
have run away with her, even killed her. But they pranced the screen full
of the Sagittarian fire, Gretel and that colt, and her smile never drew
back.

What does "full of the Sagittarian fire" describe here? The published
translation interpreted it as modifying the word "screen", which I don't
think is correct.