She made the comments after the tech giant reported mixed quarterly earnings Thursday as sales slid 7 percent from the year-earlier period.
"Our markets are moving at lightning speed, both the enterprise market as well as the printing and PC market, and we need to be faster, we need to be more nimble, we need to have a cost structure that is appropriate for the competitors that we face in both those businesses," she told CNBC's "Squawk on the Street."
Hewlett-Packard will separate its legacy computer and printing business from its enterprise computing segment. The two companies will be called HP Inc. and Hewlett-Packard Enterprise, respectively. The company expects about $1 billion in synergies and at least $400 million in dis-synergies from the split.
Read More HP posts mixed quarter as sales fall 7%
"A billion dollars was roughly what I expected. I was pleased that the dis-synergies were as low as they are." Whitman said. "I was pleased we're going to be able to offset that cost, a little bit more than half of it in '16, and then more than all of it in '17."
The company posted fiscal second-quarter earnings of 87 cents per share as revenue fell to $25.45 billion from $27.31 billion a year earlier. Its shares rose more than 1 percent in extended trading Thursday. HP was up over 4 percent midmorning Friday.
Wall Street had expected the company to deliver earnings per share of 85 cents on $25.64 billion in revenue, according to consensus estimates from Thomson Reuters.
Hewlett-Packard has not reported revenue growth in 15 of the last 16 quarters, a trend Whitman said the tech giant intends to reverse after the split.
"My view is both companies should grow, probably Hewlett-Packard Enterprise a bit faster than HP Inc.," she said.
The company also faced significant currency headwinds in the latest quarter due to the strengthening dollar, she added, noting that 65 percent of HP's business is abroad, and half of that is in Europe.
"When we raised prices to cover some of the currency headwinds, of course that has a dilutive effect on demand, so really this currency hurts us in a couple of ways," she said. "One is obviously we get less dollars than we had, but it does reduce demand because our customers are paying in local currency."
Hewlett-Packard also announced this week it is selling a 51 percent stake in its China sever, storage and technology services unit for about $2.3 billion as it restructures its business in that country.
HP says it will sell the controlling stake to Tsinghua Holdings, part of state-owned Tsinghua University, and create an entity called H3C. HP will maintain ownership of its other entities in China, including business services, software, HP Helion Cloud and other operations.
Whitman said it was important to be part of the Chinese business community and have connections to the government to succeed in the country. She continued to say the joint venture with Tsinghua will bring HP into that community and give the company access to the university's "tremendous research capabilities."
"We saw an opportunity to combine, form a JV, with one of the most prestigious institutions in China, which is Tsinghua University," she said. "If it were in the United States, it would almost be a combination of Harvard and MIT. It is the premier university in China."
—CNBC's Jacob Pramuk and The Associated Press contributed to this article.