Shamima Begum, who left the UK for Syria as a teenager, says she will regret joining the Islamic State group for the rest of her life and has offered to help the UK fight terrorism.
She told the BBC she could be "useful to society" and it would be a waste to let her "rot" in a Syrian camp.
The 22-year-old is accused of playing an active role in IS - she denies that.
Sajid Javid is standing by his decision to revoke her citizenship.
Shamima Begum was 15 when she and two other east London schoolgirls travelled to Syria to join IS.
There, she married a Dutch recruit and lived under IS rule for more than three years. In 2019, she was found, nine months pregnant, in a Syrian refugee camp. Her baby later died of pneumonia and Ms Begum said she had previously lost two other children.
The then-Home Secretary Sajid Javid stripped Ms Begum of her UK citizenship on national security grounds.
Ms Begum has previously said the 2017 Manchester Arena bombing, in which 22 people - some of them children - were killed in a bombing claimed by IS, was similar to military strikes on IS strongholds and called the terror attack "retaliation".
Asked by BBC reporter Josh Baker how it made her feel to think back to being part of a group that committed genocide and murder around the world, she said: "It makes me sick to my stomach really. It makes me hate myself."
In the interview for BBC Sounds and BBC 5 live, Ms Begum also said she only now felt comfortable talking about her true feelings.
Our reporter asked whether she had changed her opinion on IS because it had not created a caliphate.
"I have had these opinions for a very long time but only now I feel comfortable to express my real opinion," she replied.
She said if allowed back into the UK, she could advise on the tactics used by IS to persuade people to go to Syria and could share ways to speak to people who are at risk of being radicalised.
She said she felt "an obligation" to do so, adding that she did not want any other young girls to destroy their lives like she had.
On Wednesday, Ms Begum spoke to ITV's Good Morning Britain and made a direct offer to Boris Johnson to become "an asset" in the fight against terror.
Speaking from a Syrian refugee camp, she said there was "no evidence" she was a key player in preparing terrorist acts and was prepared to prove her innocence in court.
"I know there are some people, no matter what I say or what I do, they will not believe that I have changed, believe that I want to help," she said.
"But for those who have even a drop of mercy and compassion and empathy in their hearts, I tell you from the bottom of my heart that I regret every, every decision I've made since I stepped into Syria and I will live with it for the rest of my life.
"No one can hate me more than I hate myself for what I've done and all I can say is 'I'm sorry' and just give me a second chance."
She said she would "rather die than go back to IS" and added: "The only crime I committed was being dumb enough to join IS."
Ms Begum says she wants a trial, saying she is "willing to go to court and face the people who made these claims and refute these claims, because I know I did nothing in IS but be a mother and a wife".
But Sajid Javid, now health secretary, suggested there was no likelihood Ms Begum would be allowed to return and fight her citizenship case.
He told GMB that the decision to strip her of her UK citizenship was "both morally right, absolutely right, but also legally correct and the right one to protect the British people".
"I won't go into details of the case, but what I will say is that you certainly haven't seen what I saw," he added.
"If you did know what I knew, because you are sensible, responsible people, you would have made exactly the same decision - of that I have no doubt."
A Home Office spokesman said: "The government's top priority remains maintaining our national security and keeping the public safe."
Liberty, a human rights group, previously called the decision to revoke Ms Begum's citizenship "an extremely dangerous precedent" and said the right to a fair trial was not something democratic governments should take away on a whim.
One of the other girls who travelled with Ms Begum, Kadiza Sultana, was reportedly killed in a bombing raid, but the fate of the third - Amira Abase - is unknown.
Ms Begum has previously said her husband had been held in a prison where men were tortured and had surrendered to a group of Syrian fighters.
Josh Baker from the I'm Not A Monster podcast spoke to Shamima Begum for a forthcoming BBC Sounds and BBC Radio 5 Live podcast series.