More than two decades after a museum was first mooted, she felt relief, more than anything, at the opening - but said there was still a lot more work to be done.
The trust had been frustrated with delays since it was set up in 1986.
Marion Aubrey was instrumental in setting up the Mount Cook Museum Trust in partnership with the Aorangi Parks and Reserves Board.
The early trustees had great expectations of building a fine museum and started with two acquisitions - a commissioned model of climber Freda du Faur and a carving by Dick Whiting.
She said it was interesting the Department of Conservation at Aoraki-Mount Cook was reluctant to release those assets to the new trust.
When contacted yesterday, Doc area manager Richard McNamara said he would discuss Mrs Middleton's concerns with her.
Due to lack of progress, Mrs Middleton said the partnership was dissolved and a new trust - the Aoraki-Mount Cook Museum Trust - was formed in partnership with the owners of the Hermitage hotel in 2004.
Twenty-two years after the idea of opening a museum was raised, many promised items had disappeared, although other treasures were turning up to make it one of the most interesting in the country, Mrs Middleton said.
Although the museum was about a quarter of the size she had initially imagined, she was grateful it was a home for the artefacts.
More still had to be done, including providing a proper archival area where records could be kept.
Hanging above the display area is the first plane to be fitted with retractable skis for landing on snow.
Mrs Middleton's father, Sir Henry (Harry) Wigley, designed the skis and made the first landing on the Tasman Glacier in 1955.
His father, Rodolph Wigley, drove one of the first two cars to the Hermitage in 1906, arriving very early in the morning, to prove motor vehicles could provide a scheduled service from Timaru.
At the opening of the centre, one of the owners of the Hermitage, John Davies, said that for nearly a century, two generations of the Wigley family made an "enormous contribution" to the development of the area.
For Mrs Middleton, who now lives in Wanaka, Aoraki-Mt Cook was a very special place.
Not only was there her family connection, but she and her husband, Don, lived where the village was now for seven and a-half years when he worked as a ski-plane pilot.
"A terrific lot of people have been infected by the area. I still get a wonderful feeling when I come back in the mountains and look up at Mt Cook," she said.
Mrs Middleton, her brother Brian Wigley, and sisters Annabel Elworthy and Paddy Maling attended the opening on Thursday, while another sister, Jo Watson, could not make it.
