Why not just mail the traffic ticket to her home address? They already had her driver’s liscence and had written down her name and address.
The answer to your question is common knowledge and has been provided several times on this thread as well as in the linked article.
Here it is again:
Signing the citation is a promise to appear. Then if the person cited breaks their promise and fails to appear, the court can issue an arrest warrant for failure to appear, which a separate and more serious charge.