Does she need to return to respond or during the divorce process?

In order to answer that question, much more information would need to be known in order to determine whether your state has jurisdiction over her. You need to consult with an attorney.

Generally, it will depend upon the types of issues in dispute in your case. In many instances, parties reach an amicable resolution and only one party has to physically appear before the court for the final hearing. In contested matters, it is often necessary to appear to testify at hearings, at depositions, and at trial, though it is sometimes possible to appear at depositions, hearings and other proceedings via telephone, computer (e.g. Skype, Yahoo video chat, etc.), video link, etc., and much will also depend upon whether she is represented by counsel. You should consult with your attorney to discuss the specifics of your situation and your options.

She does not need to return to respond to the divorce papers. She can do that from where she is. You need to get an attorney. This will not be the only question that you are going to have, and it is best to have a local attorney on your side for matters like this.

Talk to your attorney. Some matters require her physical presence, others do not. The Judge makes the final decision. In my jurisdiction I have had appearances, and trials, vis telephone and Skype.

She is required to respond if not then apply to the court for a default. Use of a lawyer is recommended.

Whether or not she returns should not stop you from moving forward with your divorce. If she does not respond to the divorce papers, you may proceed to file a default against her and request the Court to award you what ever property and custody of the children you desire. Good luck.