peeling off of a CK t-shirt

Good day

my Sister Vuyelwa bought a t-shirt on the 12/02/2022 , she wore it and spilled something on the t-shirt which caused a stain . when she tried to wash the t-shirt the writing on the t-shirt peeled off . on the 16/02/2022 she returned the T-shirt n the store for refund/exchange but was told it would be sent to the assessors . the assessment came back to say it is not the manufactures fault that it peeled off and would not be refunded . but how is it her fault if she washed it and it just came off . now the excuse is that she worn the t-shirt . yes she did but now when she washes it . the writing peeled of and this is the fault of the manufactures