Both options are going to involve a bit of hope and luck at the moment. Some "batches" (shipping units, not the juice) will move more quickly than others; some will just sit around waiting for unused transportation room. If your liquids end up batched with stuff that has a real priority attached, you'll get it fairly quickly; if it's in with a lot of "this can wait" stuff, it could be sitting on a way station floor for a long time somewhere along the way.

If there's any way to wean your mum off of the ready-made, this would be a great time to do it. Even with al of the grumbling we all like to do about shipping times and so forth, we've really been enjoying some unreasonable reliability in what turns out to be a very fragile supply chain for the last few years. Stuff from China is cheap and local... tends not to be. DIY mostly fixes that (but you knew that already). It's not until you suddenly can't get the thing you want at the price you want that reality steps in, coughs politely, and announces its presence. If your mum's competent, that ought to be enough. If you're dealing with dementia at any level though, well, you've got some hard work and hard feeling ahead. (I say that as someone who has been through intermittent Parkinson's-associated dementia myself - that's been absolute hell on the people who care about me.)