You need to immediately take the lawsuit to an attorney to make sure you don't miss the 30 day deadline to file and answer or other pleading and have a default taken against your mother. That attorney will answer your other questions.
The above is general legal and business analysis. It is not "legal advice" but analysis, and different lawyers may analyse this matter differently, especially if there are additional facts not reflected in the question. I am not your attorney until retained by a written retainer agreement signed by both of us. I am only licensed in California. See also avvo.com terms and conditions item 9, incorporated as if it was reprinted here.