Hi, Welcome to HealthcareMagic Forum.
Does she have the same patch on he inner cheeks, roof of her mouth or gums? Is she fussy or irritable? Are you breast feeding her? Your Kid is having a Oral thrush
, Kindly take her to a Pediatrician
so that he can examine her and confirm it. If you are breast feeding her, you both should be treated. Your doctor may prescribe her a mild antifungal medication and an antifungal cream for your breasts. If she feeds from a bottle, rinse nipples and pacifiers in a solution of equal parts water and vinegar daily and allow them to air dry to prevent fungal growth.
I Wish her Good Health, Take Care.