Should the questioner's relative repeat her prayers that she performed in a shirt with an image on it, and would her prayer be valid if she concealed the image with a prayer garment?

Your relative's prayer in a garment with images is valid, although scholars dislike clothing with images. The Hanafis and Malikis consider it disliked (makruh), and according to the Hanafis, this dislike is removed by covering the image. The Shafi'is permit wearing clothes with images, as wearing them is considered a form of debasement for the image. As for the Hanbalis, their opinion varied between prohibition and dislike, citing the hadith "except for an imprint on a garment."