(assuming the posts in question follow the canonical origins of the characters, of course)

so artificial familial relations like that of Nora and Jenny Wakeman don't seem to be tagged consistently. with the example case sometimes being tagged as just mother and daughter, one time tagged as adoptive mother and daughter, and most of the time just tagged with nothing _{(which is how other similar cases, like Shadow the Hedgehog's family unit, were as well)}.

to me, personally, mother and daughter would seem like the least wrong option, but I still feel a bit sketchy on that. the creation of some sort of creator_and_creation_(lore) tag might help a bit, but with instances of characters still using common familial terms, it'd feel odd to not include a set of those existing tags (also you still have the problems of siblings).

If they share a mother_and_daughter bond, then they are tagged as such. It does not matter how one is created.
If they are canonically referred to as an "adoptive family", then you can also tag them as adoptive_mother_(lore) and adopted_daughter_(lore).

I don't see a need for a creator_and_creation_(lore) tag, unless people want to tag/see more of Geppetto x Pinocchio, Frankenstein x his monster, or God x Adam & Eve kind of relationships.
Regardless, you will still see some overlap with parent_and_child if they are canonically depicted as having such a relationship.