It depends on the wattage of the personal blender. If the motor runs at less than 450 watts, I would not recommend using frozen fruit because it will often not be blended fully and will come out as icy chunks in the smoothie. Over 450 watts, and frozen fruit should liquefy just fine like regular fruit. There’s a small chance frozen fruit could damage the blades on lower-end personal blenders, so it’s a good idea to thaw the frozen fruit at room temperature for a few minutes if you’re using one of those.