Haruka was going to forget about them when she's going to Weatherleah to show off her shining Escutcheon of Chorrol when it's starting to rain. So she went to Hackdirt, to find a shelter for her poor horse, only to find one of them found out about her and start hacking her poor horse.
Haruka ran away and decided to burden her horse by going straight to Weatherleah and never look back. It's at that time she can't stand them anymore ("Why my horse?!"). After she finished her business, she went back to Rosethorn Hall, greeted Eyja, went up to change her clothes (black shirt, pants, gloves, cape, hood, and mask) and secretly went to Hackdirt.
So she went to their silly Chapel, sat down like a good girl and waited for them. They went in, probably to offer some prayers to their silly Deep One which won't help them that night, only to find a stranger sitting on the front bench. They tapped her shoulder and asked her to leave, they didn't even asked her name! So she didn't say anything and began slashing her dual short knife like an enraged assassin that she was. They screamed "OUTSIDER!" and fought back. Long slashes short, http://upload.kapanlagi.com/show.php?photo=20101213001412_ScreenShot36_4d0502e4ea40c.jpg.
Okay, that last paragraph was made up. Haruka arrived at around 2:00 am and couldn't find anyone anywhere, so she went to the caverns and shot them one by one stealth-style with her trusty arrow and bow (this particular bow was actually meant to be a ritual bow, now it's assassination bow, whatever), each resulted in instant death, and she spared only Jiv Hiever (Haruka won't forget good deeds). However, for some reason two brethren were outside, so she had to hack and slash under broad daylight, not that anyone else was watching :shrug:. But work with me and pretend the scenario is true.
Eh, now she feels better. Looks like she didn't join Dark Brotherhood for nothing