"My targets didn't deserve them. No one does," she said. "Many of them needed empathy, kindness, understanding and support, not my meanness masquerading as a kind of casual, edgy humour. I was a troll, full stop. And I am so sorry."
The star said she'd thought it would make her "cool and relatable" to mock other celebrities online, believing she needed to impress people to be "accepted".
But looking back on her behaviour, she admitted the things she said make her "cringe" now.
"There's no justification for my behavior. I'm not a victim here. The subjects of your sympathy - and mine - should be those I put down.
"The truth is, I'm no longer the person who wrote those horrible things. I grew up, got therapy, got married, had kids, got more therapy, experienced loss and pain, got more therapy and experienced more life. AND GOT MORE THERAPY."
Teigen said life had made her more empathetic and understanding of what motivates trolling.
"[It's] the instant gratification that you get from lashing out and clapping back, throwing rocks at someone you think is invincible because they're famous. Also, I know now how it feels to be on the receiving end of incredible vitriol. Believe me, the irony of this is not lost on me."
And she and her husband John Legend are trying to "preach kindness" to their children Luna and Miles.
"Will they eventually realize there is some hypocrisy there? I certainly do," she wrote of her kids.
"But I hope they recognize my evolution. My goal is to be so good that my kids will think this was all a fairy tale. We are all more than our worst moments."
She concluded not by asking for people's forgiveness but for their "patience and tolerance".
"I ask that you allow me, as I promise to allow you, to own past mistakes and be given the opportunity to seek self improvement and change.
"Phew. A lot, I know. Thanks for listening."
Teigen initially issued a public apology to Stodden on Twitter in the wake of her resurfaced tweets.
