First, it's important here to address the problem and not attack the person, because she may be swamped by emails, all of which are deemed important by their senders, thus making prioritizing them difficult. So I suggest letting your associate know how important her input is and that you don't want to exclude her because she doesn't respond.

Once you feel you've made her aware of her significance, the next step is to actually fix the dilemma. Get your colleague to participate with you in recommending a solution. Ask her what she needs from you so that when you send an email in the future, she will respond in a timely manner that lets you move forward with your work. By inviting her help, you are showing her that you acknowledge the situation isn't her fault and that you consider her contribution vitally important to your program. By employing this approach, you will also demonstrate a crucial quality of leaders: focusing less on blaming the person and more on repairing the problem.E