I do not think Holmes was competent enough to understand that tech would never work (this is still up for debate though, "never" is a very broad timeframe).

Instead, she did waht every CEO does - hired people whom she believed to be capable of making the tech work, gave an optimistic world view to the investors to make sure she has the time/money to get to production, and demanded the results from her employees.

If anything, she was too successful - she got too much money, and she got Walgreens to agree to a test run way too early. The rest is textbook Silicon Valley.