Dyva wakes in a bed of fine silks, entirely unready to start her previously-planned day of gardening and terrorising her underlings. She considers for a moment - if she's going to be gone a year, she needs to make arrangements. How many can she get done before her parents notice and decide to confront her about it? Not enough, so she'll have to prioritise.
First priority: Her garden. Packing an entire botanical garden would be prohibitive even without mass or volume limits; it is after all, set into the earth, and it takes several human sacrifices per year to keep it at it's current level of supernatural fertility. So she has to prioritise, make sure she brings enough to work with and that the family gardener-mages won't mess anything up while she's gone. The latter should be fine - some of them have been tending that garden for generations, so it's only her most personal projects which will be at risk of neglect. They won't travel ("pet-like plants" indeed), but she should be able to order them looked after while she's gone, and in the mean time she can have the contents of potting shed three put into crates for her so she has tools to work with while she's gone.
(As she thinks, she gets out of bed, has a maid start fixing her hair and makeup, and generally prepares for a busy day).
Second priority: Her belongings. She doesn't have anything she's incurably attached to which isn't secure in her room (One of her teachers destroyed any possession of hers that she *didn't* keep secure, to teach her paranoia.), so having everything packed, along with enough good clothes for a year's travel, should be simple. The problem is, her parents will noticed all the crates and suitcases forming. Does all her luggage need to be in the same place?
Third priority: Travel goods. She can ask one of the senior staff to suggest any items she'll need while travelling that she wouldn't while at home. Not until everything else is packed, though, they'll tell her parents.
Fourth priority: The vaults. Is there anything worth getting out of the family vaults for this? Probably not - the trip is all-expenses-paid, so she shouldn't need absurd amounts of money (Merely the very large amount she can get from her own rooms), and the letter said not to bring cursed items with her, which rules out nearly everything else, even the most useful things. And if she needed to unleash a demon of excess upon her foes, it'd be a pretty bad pleasure cruise, demons are terrible.
Properly dressed, and with everything planned out, she heads off, sending all of the orders which will need to be sent for her luggage to be collected. The staff are surprised, but obedient.