The formation of ice crystals on/in frozen food that has been defrosted and then frozen again
Industrial ice cream makers make it frozen much faster than household freezers. They freeze faster and ice cream is disturbed to take out heat and to keep the emulsion well dispersed. As result, frozen water based emulsion droplets are very small.
When melted and standing, emulsion slowly separates either and oily phases.
She put in household freezer, it is getting frozen very slowly. That helps further emulsion separation and ice have enough time to form big crystals.
Note that it happens for frozen vegetables as well, if melted and refrozen again. Without any added water.