Pam Westbrook and her family have spent more than three years and £45,000 to make Hannah's Holiday Home a reality.
The home has been set up in tribute to courageous 10-year-old Hannah, who lost her battle against Hodgkin's Lymphoma three years ago.
EastEnders actress Emma Barton, who plays Honey Mitchell in the BBC soap, was on hand to cut the ribbon at the grand opening.
Emma, who was born in Portsmouth, met with the first visitor to the home, six-year-old Tatum Kemp, who suffers from the rare lung disease interstitial pneumonitis.
Mrs Westbrook, 38, of Nightjar Close, Horndean, described how she wept tears of joy as she saw what happiness Hannah's legacy had brought Tatum and her family.
She said: 'We had more than 100 people turn up and raised at least another £350 on the day.
'Emma was just lovely when she met the Kemp family and the kids.
'All the children knew exactly who she was and were quite excited. In fact, so were the adults.
'Tatum had a whale of a time – she was just racing from room to room, with her dad behind carrying her oxygen tank and struggling to keep up.
'We were so happy it was such a success. And the weather stayed gorgeous – that was Hannah directing it for us, I think!'
The holiday home is at Oakdene Forest Park in the New Forest, a 55-acre complex specially built for families.
Tatum's grandmother Jenny Kemp, 56, from Clacton-on-Sea in Essex, said: 'It really is everything we could have hoped for and more.
'Tatum has just loved it.Her favourite thing though has been the swimming. We just couldn't get her out of the water.
'And when Emma visited she stayed for ages and had all the kids on her knee.
'Tatum just thinks it's a shame we have to leave. It's terrific, and I just hope the next family enjoys it as much as we do.'