Having two "Princess Colognes" on the field makes it impossible for the opponent to attack.
Neither "Cologne" can be the target of an attack nor card effect. The only way around the lock is to destroy her indirectly with some sort of board wipe, such as "Dark Hole", "Raigeki" or "Black Rose Dragon".
If there is a Level 4 monster on the field, "Rescue Rabbit" can be used to Special Summon two more Level 4s, then use one of the Normal Monsters and your other Level 4 to Summon this card. At the end of the turn, when your other Level 4 is destroyed, a powerful monster like "Blue-Eyes White Dragon" or "Millennium Shield" can be searched out.
Equip "Buster Rancher" to "Princess Cologne": not only "Princess Cologne" is virtually impossible to stop and cannot be targeted by effects or attacks due to her own effects, but if she attacks the opponent's monster with 2500 ATK or 2500 DEF or more, "Princess Cologne" will easily destroy most of them. Having a card such as "Trap Stun", or a card such as "Shadow Spell" that reduces the ATK or DEF of your opponent's monster(s) can make it easier to destroy them and eliminating threats that would otherwise destroy "Princess Cologne", should she actually be on the offense.