Whatever Queen Fabiola might have resented in Princess Lilian, it is such a long time ago and as a devout Catholic she must know the concept of forgiving and the soothening of mildness.
I can not imagine that Queen Fabiola still does not wear jewels because Princess Lilian once wore these. After all she has worn jewels which were worn by her mother-in-law: the Empire Diadem comes to mind.