Once you manage to summon The Unhappy Girl, start attacking Joey's monsters to prevent them from being able to attack. For the Holy Guard skill, you won't receive any battle damage only during your turn.
It's a glitch. You can trigger it by choosing a character in the character menu and just before everything loads as it should you press back on your hardware button (samsung mostly) and since the game does not load correctly you end up with the last characters skill you used.I actually hate that glitch.
Uff..the only way I see replacing double summon is careful planning. Get 2 UHG's locking down the field, they would need to each hit all 3 of Joey's faceups. 1 turn before kill shot, summon Pirahans' to 3rd slot (don't attack with them). Last turn summon BEWD using your 2 UHG's. You do risk Joey throwing a wrench in things but ...doable.
Another option you could possibly do is run black luster ritual. Substitute the double summon for the ritual, instead of BEWD run a 7 star. Then you have to cut 1 more card, I opted to cut hieroglyphics. But that's bc I don't have the card. There might be a better card to cut.
Final turn, do it in this order:
Secret pass -> piranha
Storm (if he has metalmorph or kunai with chain set, he will activate them, that is why you use secret pass first. If he has metalmorph and all his monsters are loced by the unhappy girl, he will target your piranha making it an 1100 which is to much for secret)
Tribute summon Blue-eyes (not using piranha as a tribute)
Riryoku -> blue-eyes to piranha
Gift of the martyr -> tribute blue-eyes
Enter battlephase and attack directly with piranha