In A Favorita (2018), Before she took that ride on the horse, Sarah was poisoned by Abigail. The poison's effect showed on Sarah, who as a result fell on the ground and was dragged by the horse. She returned to Anne late, lied to her that she had a battle on her way back instead of ever revealing to her that she was poisoned by Abigail.
Why didn't Sarah tell Anne that Abigail had poisoned her?