Abused a girl very badly, what to do now??

19 M, When I was 14 years old, I abused a girl very badly, I messaged her on Instagram, with some very derogatory and filthy words, probably the most devilish language I ever used.
Now whenever I remember that incident, I feel deeply embarrassed and pathetic.
I want to apologize to her but won't she think I am trying to be in some relationship again or do something creepy to her?

PS: Here's what I did--" She broke up with me, giving me a fake reason that our academics were getting disturbed, but in reality she got a new guy.
So , I as a very immature guy, DM'd her with very abusive shit, even talked about her being the Wh.., Sl.. and what not.
I didn't even leave her new guy, also messaged him something abusive."

What should I do now?