If it could somehow be shown that Luke and Leia’s sabers are broken after the Palpatine fight, that would make burying them and her making her own make much more sense. Maybe in the shots of Rey holding and dropping the lightsabers on the ground some sparks could be added coming out of the sabers, like Palpatine’s lightening fried them or something like that? Or even some smoke? Something to hint that they are broken.
It would be harder to do but maybe have them still ignited when she holds them and they both sizzle out on the ground?