She wanted to take over the Slime Kingdom and turn it into a military force to take over all of Ooo. In order to get control of the kingdom from her sister she had to get married, but by Slime People standards she was so attractive no man could work up the nerve to approach her. Therefore, she made a fake husband named Guillermo and was about to take over the kingdom until Slime Princess convinced Finn to pretend to be her husband and they eventually found out the truth about Guillermo, thus disqualifying her challenge for the kingdom's rule.
|Adventure Time Villains|
Ice King | Marceline Abadeer | Lumpy Space Princess | Gunter | The Lich | Hunson Abadeer | Earl of Lemongrab | Flame Princess | Martin Mertens | Ricardio | Death | Marshall Lee | Ice Queen | Patience St Pim | Dr. Gross | Shoko | Magic Man | Vampire King | The Fool | The Empress | The Hierophant | The Moon | Ash | Flame King | Fire Count | Don Jon | Fire Kingdom | The Guardian | Gareth | Flying Lettuce Brothers | Tiffany Oiler | Guardians of Sunshine | Ooze Monsters | Fear Feaster | Kee-Oth | Maja the Sky Witch | Darren the Ancient Sleeper | Goliad | Blargetha | Demon Cat | Guardian Angel | Wendy, Booboo & Georgy | Squirrel | Stag | Scorcher | Jaybird | Smudge | Princess Cookie | Tree Witch | Xergiok | Me-Mow | Alpha Hug Wolf | Tree of Blight | Evil Monster | Donny | The Glitch | Grassy Wizard | Fight King | Furnace | Torcho | Gnome Ruler | Sir Slicer | King Worm | Blanket Dragon | Little Dude | Cute King | Why-Wolves | The Hooligans Who Love Candles