Wulfie, I definitely hope you're watching Girl K/Killer K, since it's totally your kind of 'girl goes on a rampage to revenge family and she has excellent martial arts skills and kicks ass a lot' kind of thing :).
This is a 3-part Korean action drama from a cable channel, so it has a lot more nudity and violence than your usual kdrama. You could actually compare it to Korean movies, which feature this kind of stuff a lot. It's K-19 in Korea, but I guess it would be about K-16 in Western terms. Lots of blood, but no really gory stuff based on the first two eps.
I've only seen the first episode, but intend to continue with the rest of the two right after posting this.
Cha Yeon Jin is a teenaged schoolgirl from a poor family consisting of her and her mother. She has excellent martial arts skills and tends to react with violenge towards people who disparage her origins or her mother - or who attack her.. After getting kicked out from yet another school she's hanging out with her friends at the harbour where her mother works and sees an illegal deal that ultimately goes wrong. Almost everyone gets killed, Yeon Jin is on the run and there's this mysterious object that the killers want in exchange for her mother.
Looks like there's a lot of other behind-the-scenes stuff to contend with, but my first impression is that it's an excellent action/revenge drama and hopefully will deliver on the writing front as well. Based on the drama description, she's picked up by some kind of agency that trains her to be even better and is intent on destroying her mother's killer... Thai revenge movie/Korean revenge movie - probably a combination of both.