Now in the early chapters she seemed oblivious, but is there any reason for her to figure out those feelings just because of one stray thought years ago? It would also not help her realize Asuka's attraction to her. So as far as I'm concerned this didn't contradict the context (yet).
I'm actually not entirely sure anymore she was completely oblivious at the beginning. I mean, that's how I always read it; that she's just being motherly and kinda "accidentally" a bit flirtatious (from Asuka's perspective). That also fits with how she "acquired" her husband; presumably not by actually doing anything (from her perspective; that's why she's so surprised) but simply by being approached and accepting.
Buuut ... it doesn't actually say what she thinks when plucks rice from her daughter's cheek. And it's her that gets scared of losing Asuka and holding hands afterwards; all blushing. And when she says it's probably her fault, and she wonders when everything changed (for her), she isn't going "yeah obviously just now when Asuka confessed". It might have been supposed to be a hint that for her "things changed" much earlier.
So ... she might be oblivious to how Asuka feels about her, but I suppose it's possible that at least on some level she been somewhat aware of her own feelings from the beginning of the manga.
That being said I'm also not really convinced by this; so let's see where the story goes with all its flashbacks and so on. ^^