The Princess of Wales hailed an 'inspirational' residential centre which aims to keep women out of jail and united with their children.
Kate, 41, pinned a hand-written message to a tree which read 'I see you and I'm with you. Good luck in all that lies ahead'.
Wearing a polka dot dress, today she opened Hope Street in Southampton which is a pilot project where low-level female crooks can serve their sentence in the community rather than be jailed.
The aim of the residential centre is to offer Magistrates' the option of sentencing women who committed minor crimes such as theft or anti-social behaviour to Hope Street.
It also means mothers do not see their children put into care if they receive a short jail term and gives women a 'safe space'.
As she arrived, Kate said: "Well done it's fantastic. I love the location as well as it's not out on its own, it's in the community in many senses."
She was shown round one of the plush fully-fitted eight flats in the development - which cost £7million from private money and donors - which opened today.
Kate said: "Gosh, look at this. It's aspirational."
Hope Street is the main hub of eleven centres in Hampshire which acts as a safe place for women to serve their sentence in the community.
It is hoped that magistrates will choose the privately-funded project so low-level criminals don't clog up the prison system and women don't have their children put into care.
Residents are likely to be convicted of smaller crimes such as theft, anti-social behaviour, and unpaid fines, rather than violent or drugs offences.
It is not a bail hostel but women can live there under curfews or bail arrangements.
Kate chatted in the building's common room with two women who were among the first to get keys to a flat.
One of them was in tears as she described having her children taken into care and that Hope Street made her realise "people care about me"'.
Kate said: "I understand your story and your journey."
She added: "Just looking around and seeing the flats it's an inspirational place."
During a speech to mark the opening Lady Esther Grosvenor, founder of One Small Thing which created the building, told fundraisers and supporters including newsreader Jon Snow that she "challenged the system".
Kate pinned her message on a tree with others and walked away with Esther who had their arms around each other's waists.
Hope Street also boasts a creche and cafe.
Outside, ten-year-old Rosie Fay handed Kate a bunch of roses.
Afterwards Claire Hubberstey, CEO of One Small Thing, said: "The problem with the justice system is we have a huge number of women who have committed a crime but they lack a safe place in the community and have to go to prison.
"As a result, in these circumstances their children go into the care system."
Some receive short prison sentences and when released have lost their home, she added.
She said the aim was to end "women stuck in a circle of short sentences" and working with magistrates across Hampshire.
Women eligible have committed low-level crimes such as theft, anti-social behaviour, traffic offences and non-payment of fines.
Hope Street has room for 24 women and eight children but space for 120 women centres across Hampshire.
