You could send a DNA sample from a hen that lays blue eggs to get a test for the blue egg gene https://iqbirdtesting.com/blueeggThinking the possibility that this blue egg phenomenon with my Malays maybe a recessive mutation, so a different gene.
If they find the blue egg gene, then she has the usual form.
But if they do not find the gene, and she does lay blue eggs, that should mean she has a different gene.
Edit to add: this would probably be faster and cheaper than raising chicks to check the inheritance (cheaper because of the cost of chicken feed).