first of all, this is what can happen when you house two ball pythons together:
what your mom saw is most likely them fighting, BP's are solitary animals, get very stressed when housed together, and two males especially will fight, maybe to the death, and this might also be an outcome. i would suggest housing them seperatly asap. even though they might seem "happy" together, they are actually just tolerant of it, for now at least. and if you absolutly have to house them together, make sure theyre in a large enough, and cluttered enough space, to not feel like the other snake is invading their turf