Referring to your "similar question", when in a double-battle, the power of multi-target moves against each Pokémon is 75% the normal-value. Blizzard will NOT hit your ally, only your foes.
So, if targeting only one opponent (or if one opponent is still in battle and its ally is fainted), it will do its normal value of 110.
But, if targeting both opponents, it will do (110 x 0.75) 82.5 per opponent (rounded down to 80 (Found the Source)).