I'd say for sure she's overpaying for what it is. That said, there's a couple factors at play here. If she's not mentally competent to take care of herself anymore, that needs to be addressed and something put in place for her own wellbeing, it's not a "why are you buying junk" conversation. If she has dementia and can't function daily weekly monthly, she really shouldn't be in charge of her finances anymore, and things put into place so she has her needs met and can't spend money she needs on a whim.
if she is competent, and she's got her bills paid, she's free to blow her money on whatever catchers her fancy, even if you think it's a bad idea, it's her money and if she burns through it and there's nothing left in the estate in the end, again, it's hers to do with as she wishes. You could voice your opinion, but it's hers and she might not like your opinion on how she spends her money.
I would suggest you don't approach it from the angle that she doesn't know what she's doing, or she's being taken advantage of or getting ripped off though, it's a bad idea. She's a grown person, and may get triggered by you butting into what she likes and wants to do. It might be more productive to take interest in it and what she's doing, is she buying these items for something to pass on? or is it because she likes it herself and using that as an excuse? See what she likes about it, and steer it in a more productive direction, while you spend time with her in the process.
or if she's doing it for something to pass on of significance, maybe find out what she likes that has value and steer her in that direction going forward.
This all said, I see nothing there in the pictures that sells in the hundreds or thousands dollar range individually. All of the items pictured could be bought right now from littleton, or American Mint for $10-$20-$30 each. Maybe something that sold for like $50 tops. If she spent thousands, these items aren't it.
Not sure your particular situation and if you are seeing the charges, or she's telling you she paid a lot for them, but those items all sell relatively cheaply. I looked most of it up, these pictures are full blown retail from the sellers for around $400 for all that is pictured, and it's likely worth a quarter to half of that, maybe if it were all sold to people on ebay.
From this isn't not as bad as it sounded at first, it's bad, but it's not that bad.
As far as Littleton, they do a "coins-on-approval" system, American Mint might do the same. They mail you items, you have to send them back or they will bill you.
Simple calls to them telling them she is elderly with dementia and you will report them to authorities for elder exploitation and to remove her from any on-approval programs they might have her on, should put an end to that nonsense quickly, if she's mentally competent to take care of herself and her finances though, there's not much you can do, she can go right back to them if she chooses.
I wish you the best of luck with the situation, but I think you should tread carfully on how you handle it. My mom like the mail order catalogs and buys overpriced junk, we've had arguments over it, but she's competent, and in the end it's her money, and she's constantly going to go to the "well your brothers never come and see me, I'm by myself all the time unless you come by"
For the record, I go by daily and spend time with my mom because I know she's alone. She does the by mail catalog shopping, because it's what makes her happy during covid and hiding from the world and the tv news nonsense, and, and, plenty of reasons. and yeah, I've got crappy brothers that live close enough to stop by daily also, but don't but are gonna wish they had after she's gone, just like they wish they had spent time with my father before he passed... it is what it is.
Sorry so long winded, but hopefully I helped in some way.