At first, she thought that Mr. Stark didn't like her because she wasn't pretty enough, so Pepper changed the way she wore her make-up and did her hair. He told her that he thought she looked fantastic, but he still didn't make a move, so she was eventually forced to rule that one out. She kept on with the new style. Looking more glamorous did wonders for her self-confidence and she wasn't keen on giving that up. She wasn't being fair to him, assuming that only beauty could capture his attention.
Oh, but he was such a hottie.