I don't think so. Despite it all, her martial arts skills aren't the main point of connection between her and Saotome. In fact, the new girl being into fashion is bigger threat than her being a martial artist. Don't get me wrong, her skills are certainly part of her charm, but she's not a person...
I'm 90% sure that this manga will reach their third year in high school if it can run its course. Too many plot threats hanging in the air are dependent on this happening.
Granny was killing them with simple surprise attacks. The soul imprisonment was just to get bait for them. In fact, the Granny was always the main danger of the park, not shinigami.
Second, the salt water technique has a little purpose when you actively need your enemies to notice you to reveal...
Being fair, the nurses in the last chapter straight up said that something had to give, either her body, her mind or her heart. She's already a traumatised mess and she herself states that she lost a lot of her ability to feel in the previous chapter.
Personally, I do interpret it as an example of irony. Guy wished for a good, righteous son and got what he wished for. A kindhearted son who utterly loathes a monster like him and who directly lead to his damnation.
Dude was at best an utterly delusional monster. He got multiple reality checks and just thought that he needs to punch his "loved ones" harder to deal with them.