It's true. It is just a nice t-shirt that she likes wearing. It doesn't offend me if she wears it in innocence. I saw a young girl (aged about 8 years) obviously from a wealthy family wearing a t-shirt with "Fuxx me, you cunx, " written on it. Did she know what it meant? Obviously not.
I understand her and many Thais do the same, but and there is a "but".... there are certain designs that could be printed on a t-shirt, that if worn by a foreigner would cause a lot of commotion.