is a 3rd level spell for witches, and Mythic Deep Slumber can do what you want with a Mythic Tier 5 Witch. Mythic Tiers are independent of level so you can certainly have a 14th level Witch with MT 5. Mythic Tiers are really powerful, however, so you might want to drop her level a bit or give the PC mythic tiers of their own in the course of the quest.
Bestow Curse, a core level 3 witch spell, allows the caster to make up their own effects, but is easily removed long before level 14.
Greater Bestow Curse (from Pathfinder Adventure Path #82) is a level 7 witch spell, right up the alley of our 14th level witch, allows more powerful effects, and is much harder to dispel (will require a decent quantity of specific items dedicated to fixing this one problem on the part of the rogue, or a level 10 caster with Break Enchantment and plenty of time (or Pearls of Power V)).
Having to sleep isn't well covered by the core rules, but adventure path 44, cited in this sidebar, gives some rules. Severely affecting a character's sleep requirements is well in line with both versions of the spell, while some form of Save-or-Die sleep effect (e.g. Fall asleep, as per the sleep spell, immediately. Fort save or can't wake up until the curse is removed) would be in line with the short-range 7th level greater curse.
If there's a shortage on royalty in the area, an Apple of Eternal Sleep (from Ultimate Equipment) is exactly what you want, and very classic, but the whole 'ends on kiss from royalty' thing probably puts it out of the question here.