I think she's Korean? (KaKaoTalk). If you're still here, please let me know. As long as she's the victim, not the bully.
As for the record, I'm not an investigator or authority, I just want to help, or we may be able to help each other. Is he a lawyer? Erm.
a) If H blackmailed L, does she have evidence of it? This part is particularly problematic - "H claims to have a lot of sensitive information and webcam recordings". If L has recorded or copied that claim, why hasn't she reported it to the police? I believe there can be no better evidence than that.
b) How does L know that H knows her personal conversation, is there any other way than eavesdropping to know her conversation?
c) What school, is that a law school, or just a university which still has law major?
d) What subtle hints and how can you be sure it was about L?
e) Does L know H personally? Seriously, why hasn't she reported it to the police yet??!!!
f) It doesn't matter whether or not H has rich parents or a law student (and this part raises serious concern, since this H person seems to lack basic moral for being a lawyer).
g) If H is a webmaster of a certain website, it's definitely possible for him to hack into L's computer without hiring any people for that. Hacking is not that hard. "Social engineering" is another way of hacking, and in your case, it can be done by sending "pictures, emails" and L can simply click them and make her computer infected. And the real problem here is, this H person, who is a webmaster of a website, is doing things like this, and I bet he's doing things like this more; provided that this story is not made up or just happening in L's head. In this digital age, you never know what scary things mentally derailed people can do without leaving their room. L has every evidence she needs! She owes it to the society. Report it to the police, there's no reason for hesitation.
h) It's totally possible to know what you type on your computer, they can even monitor your monitor.
Tell me, for more details or chat.
And why I asked you c) question, because I think I can definitely help you.