"We are buying a club that could be relegated next week," she told Reuters in a telephone interview.
"If we were thinking about this as being some type of sportswashing exercise we would have made different choices."
A major obstacle to the Newcastle takeover receiving the green light from the Premier League authorities was the issue of whether the Saudi state would interfere in the running of the club.
Eighty percent of the funding is coming from the Saudi sovereign wealth fund, the Public Investment Fund (PIF), swelled by the proceeds of the world's largest oil deposits.
Asked if the Saudi state and its representatives would meddle in the club, Staveley told the BBC: "No, not at all. Absolutely not." She added: "Our partner is not the Saudi state, our partner is PIF."
But Ms Staveley said the $430 billion PIF was an autonomous, commercially-driven fund that had paid a reasonable price for a club in which it planned to invest for the long term.
Key decisions will be made by the new board of PIF governor Yasir Al-Rumayyan, Ms Staveley and Jamie Reuben, the son of billionaire property investor David Reuben - although Ms Staveley said the executive team could be strengthened in future.
Newcastle are currently second from bottom in the Premier League standings after a disappointing start to the season under manager Steve Bruce.
Ms Staveley said she had been texting former striking great Alan Shearer and former Newcastle manager Kevin Keegan, both revered on Tyneside, and hopes to offer them as-yet unspecified roles.
She will start by seeking to move Shearer's statue to its"rightful place" inside the St James' Park grounds, she said. It currently stands outside of the stadium.
"We are really excited about working with him because he's just a legend," she said after returning to London from Newcastle by train where, she added, she had been "cuddled" and photographed by fans delighted at a change in ownership that will make the club one of the richest in the world.
She now wants not only to secure new players, but ensure there are great managers, training staff, medics and physiotherapists and a beefed up academy and scouting network to attract young talent.
"Of course I want to win the Premier League," she said. "At some point, of course, we want trophies. The last time the club won a trophy was 1955.
"But this is a long-term project and it will take some patient capital," she said.
Academic James M. Dorsey, and author of The Turbulent World of Middle East Soccer, said sport is being used deliberately by countries in the Gulf to gain prestige.
"What we're seeing is a pattern where sport is part of a bigger move, a move by the Saudis to basically - in whatever sector it may be - position themselves as the top dog in the Gulf," he told SBS News.
"If you look at Saudi sports strategy over the last five years since Crown Prince Mohammad Bin Salman came to power, it only succeeded in basically paying for events to take place in Saudi Arabia.
"This is their first success - and it puts Saudi Arabia on the same par as Qatar and the United Arab Emirates in competing for prestigious assets.
He said human rights should be a part of the scrutiny process in football club takeovers.
"The English Football Association has a smell test, if you wish, which is supposed to look at if the integrity of the owner is one which should allow him to own an asset like a football club. Human rights are not technically a part of that smell test, but they should be."
Additional reporting: AFP