Michelle Young, 49, described the lump sum as "disgraceful" and has vowed to fight on to get more cash.
She originally wanted £300m from her property dealer husband Scot, 51, claiming he had a vast hidden fortune and was worth at least £1 billion.
But Mr Young, of Dundee, a friend of Simon Cowell, has insisted he is penniless and bankrupt, with debts of £28m.
Now mother-of-two Mrs Young has insisted her battle has been about equality and standing up for women's rights rather than greed and claimed she was not "bothered" by the loss of her lavish lifestyle.
She said: "This isn't about money, this is about justice and equality. It doesn't matter how much money is involved, it's about fairness. I have had so many women who have been wronged approach me. There needs to be some major changes in the law.
"I would have been happy to settle for the £300 million figure but now it's a situation where he's not going to pay and I will have to enforce. This was as much my money as it was my husband's and I will continue to fight and I will win this case."
Last month, judge Mr Justice Moor ruled Mr Young was worth £40m and his wife should get a £20m lump sum. The couple, who live in London, split in 2006 after a 17-year relationship.
Mrs Young had told the 12-day hearing at the High Court family division in London she would settle for £300m and wanted a £25m home in the city's Belgravia.
Details of the couple's lavish life were aired in court. It was claimed that Mr Young would spend up to £5000 in a restaurant, that he paid at least £2m for "a flash gin-palace" boat and that Mrs Young had jewellery which was said to cost £1m.
The family had several homes and previously owned Woodperry House, a mansion in Oxfordshire.
Mrs Young insisted she had adjusted well to the end of her lavish lifestyle but said she owed it to her two daughters to fight on.
She said: "It's been absolutely devastating for the girls, I'm absolutely appalled that their father has allowed this to happen.
"We have downscaled by a huge amount in our lifestyles but that hasn't really bothered me so much because I am one of those people, I just face whatever comes along.
"But for the sake of my children I have to bring justice to my case and get the money that has been hidden."
Mr Young, who denies his estranged wife's claims of hidden wealth, was jailed for six months earlier this year after he refused to reveal details about his finances.
He has been given until December 20 to pay the £20m and his ex-wife's £5m legal costs.