Dynamic stretches for warmup

She is right on.  Dynamic stretching prior to events has been shown to improve athletic performance.  For all the reasons she elaborated on. 

 In contrast, static stretching has been found to be detrimental prior to event because it causes small muscle tears in cold muscles.   Save the static stretching to cool down sessions, post workout.  Thats when this type of stretch is beneficial.  The reason for this is that you've likely torn the muscles through working out.  The static stretching helps the tissue get back into alignment, allowing it to heal/recover faster/better.