First off, she didn't write the speech. She picked the wrong person to do it. And considering she is not even the candidate or even going to be holding any office in the administration this is a non issue.
Not an official office, but since the days of Eleanor Roosevelt it's a position with a great amount of power and influence.
The primary reason Colin Powell didn't run for President is that he didn't want to expose his wife to the visibility of being First Lady due to her chronic depression. Had Powell chosen to run, he would have easily been the nominee over Dubya, and the country far better off for it.