Thank you so much for sharing your observation with us. It is a female cardinal with a feather variation caused by leucism. Leucism is a condition characterized by reduced pigmentation in animals.
Right now scientists describe two kinds of Leucistic birds, pale and pied. Pale leucistic birds will have the same markings, but extremely pale. Pied Leucistic birds, like the one in your photo, have patches of white. Leucistic birds are relatively unusual but much more common than albino birds which are completely white with pink eyes, legs and bill.
Unfortunately they usually don't have as long a life span. It doesn't affect their health but they are easier for prey to spot and have a harder time attracting mates. So consider yourself lucky!
Read more at Project Feeder Watch's website: Plumage variations: Albinism or Leucism?