I quickly translated this. It may help you. The Harionago is from western Shikoku. I left the Japanese there in case I missed something and anyone would like to correct me or read it themselves. From what I get from this story, she laughs at the boy in that sort of "he's not good enough" way, but if he laughs/smiles back, she gets angry at them. Also, in Japanese, the word for laugh and smile is the same word, so maybe the boy is merely smiling back at her?
(From:
http://youkaibiyori.blog80.fc2.com/blog-entry-1642.html )
針女(はりおなご)
Harionago (Hook-woman)
四国の宇和島地方(愛媛県)の妖怪。
「ヌレオナゴ」または「笑い女子(わらいおなご)」ともいう。
A youkai of Shikoku's Uwajima area (Ehime prefecture)
It's also called "Nureonago" and Warai-onago (laughing girl).
ざんばら髪の先に、鉤針のような鉤がついていて、
これで男を引っ掛けて連れて行ってしまう。
この鉤を引っ掛けられると、いかなる大男も身動きできなくなってしまう。
It uses hooks at the end of its hair, ensnares the man with them and takes him away. If ensnared, even a great man can't move about.
城辺町の桜岡は、「針女」がしきりと現れて、
若い男を苦しめるところであった。
ある晩、山出村の青年が1人でここを通りかかったところ、
向こうのほうから美しい娘がやって来た。
ニタリと笑うので、すこし気味悪く思ったが、美貌につりこまれて笑い返した。
すると、長い髪をふり乱して襲い掛かってきた。
青年は驚き、一目散に家へ逃げ帰ると、
大戸を閉ざしてぶるぶるとふるえていた。
夜の明けるのを待って恐る恐る表へ出てみると、
大戸には、髪の毛の先で引っかいた無数の疵あとが残っていた。
大戸が板戸であったため、危うく難を逃れたのだ。
それからというもの、「針女」に追いかけられたら、障子戸ではなく必ず板の大
戸を閉めるようにというのが教訓となった。
In a village near the (Matsuyama) castle, Sakuragaoka/Sakuraoka (there's a place called "Sakuragaoka" with that kanji in Shikoku, but I'm not sure), there is frequent sightings of Harionago, which are places where young men have suffered.
One night, a boy from Yamada village happened to pass by this place, and a beautiful girl came walking in the opposite direction.
Because she was smirking and laughing, he thought there was something uncomfortable about her, but he was taken by her looks and returned a laugh/smile.
When he did, her hair fell down in disarray and rushed at him.
The boy was alarmed, and as fast as he could, he ran back to his house, closing the door trembling.
He timidly waited until dawn by the front door. There were scratches left behind by the countless number of hairs caught in the door.
Because it was a wooden door, he barely escaped.
After that, if a boy was chased by Haraionago, the lesson was it was necessary to shut the main door and not the sliding-door (ie. so the hairs couldn't get through the door).
広見町とか三間町などでも、
道を通る男にニタリと笑いかける女や、すこし気の狂った薄気味悪い女に会った
ときは、
女の笑いにつられて笑顔を返そうものなら、一生執念深くつきまとわれるという
ので、要注意とされている。
しかし、これは、
「やかましい」
と一言、大声でどなってやると消えるという。
Even if you're somewhere like Hiromi village, where there is a distance of three villages (to the next one? Not sure; I don't know Hiromi either), if you (a boy) is walking down the road and you meet a smirking, laughing girl that gives a slight maddening and eerie feeling, and if you're taken in by the girl's laugh and return a smile, you need to pay special attention to the fact that she will spitefully follow you.
But, if you yell in a loud voice, the single word, "Fussy", it is said to disappear.
<参考文献>
「図説 日本妖怪大全/水木しげる著」
<Work Cited>
"Zusetsu - Nihon Youkai Taizen" - Mizuki Shigeru-cho
"Illustration - Encyclopedia of Japanese Youkai" - by Mizuki Shigeru