Summon Unhappy Girl, or Rai-Mei if you don't have unhappy girl, and stall until you can perform gravekeeper's vassal and union attack combo. Set a Rai-Mei when you set an Enchanted Javelin to raise your LP to ensure Tea won't attack the unhappy girl while also thinning your deck. Summon BEUD when you can before the last turn and leave 1 monster slot open for vassal.
Example deck (No Union Attack)
Works similarly to the method above, except the finisher is Cu Chulainn. Use the Rai-Mei to thin out your deck and summon BEWD early in the duel. Since Cu Chulainn's damage is only going to be around 5000, make sure to destroy her solemn wishes as early as you can, otherwise just deal the 5000 damage and get her to deck out.
I cant post my Deck screenshot :(
But here's my deck:
SKILL: ELEMENTS UNITE!
×3 Thunder dragon
×1 Piranha Army
×1 Gift of The martyr
×1 shard of greed
×1 goblins secret remedy
×1 hieroglyph lithograph
×1 secret pass to the treasures
×3 pot of benevolence
×2 remove trap
×3 jar of greed
×1 twin headed thunder dragon
×1 flameberg baou (purely space filler, block skelengel
For Tea you MUST have blue eyes ultimate dragon or master of oz as she has 2 traps cards that give her 500 life points every card she draws but for Yugi, Odion, Weevil and Rex you don't need a fusion monster, you only need gate guardian which you get at the beginning.
You could use something like this for Yugi, Odion, Weevil and Rex as they don't have cards that gives them life points but for Tea you must use something like the deck above as she gains life points. That max I've seen her have is 14k.