@Sep10trion i don't think they do. I'm guessing that divine embroidery is one thing and the spirits help is something like an add on because of how strong the mc powers are
@Sep10trion: Doubt it, if you remember the spirits were wearing rags initially, and only after being gifted new 'clothes' (read: mana) by Ewey are they this active/happy.
In all likelihood the spirits were around, but nobody in the family could see/interact with them so they couldn't do anything but just wait around.
Side note: She kept the spider? You'd think the family would take it away from her if they think of her as such a useless person...
I wouldn't doubt the possibility that their greedy hearts is what kept them from being able to see the spirits, and over time the family became so egoistic/greedy that they couldn't do a proper DPE and so do what they can (imbue their own magic to the threads) and pass that off as the real thing just that they're not as strong as the founder.
Though that idea is partly from reading far far ahead in Bookworm
Where due to the action of a certain queen in the past, the traditional methods were forgotten and over time the quality of magic users dropped due to not realizing they're doing it wrong.
The MC did things the 'right' way, though not intentionally, and became very powerful for it.
EDIT: For anyone who care, here's the RAW for the WN, which just from the quick skimming I've done has some difference to this already.
https://ncode.syosetu.com/n0020by/
@WhimsiCat I would assume that since Ewey couldn't do Divine Protection back then with the spider, the spider became equally useless, thus only good for making regular dresses.