The President didn't pull her from anywhere. She begged the President-elect and promised with tears in her eyes she'd be an asset for the administration's outreach to blacks. He gave her a chance.
Omarosa latched onto Trump from the minute she saw him. She saw him as the path to somewhere on her road to relevancy.
When he was actually elected, she took advantage of her prior connections with him to get a job in the administration. As you say, she literally begged for it.
Trump did not make a good decision on this and he certainly knows that now. And he will learn from it.