This was a very strange arc, there has to be more to this "yandere phase" than what we were let on.
The smile Ichika had near the end of the chapter, and considering she used her info-gathering skills to place Miku and Fuutarou in the same group, It didn't seem like the smile of someone who was just exposed and had all her plans fell into ruin.
I don't think she had a "last moment regret" either, I think that, while she IS in love with Fuutarou, she had something else in her mind all along.
I know that this is some 4D chess bullshit, but if there's a character that makes sense to have such a convoluted plan it has to be Ichika.
I mean, the other option is accepting this strange arc with this strange antagonist that didn't accomplish anything and knew she would "fail".