You can sue if the statute of limitations for oral agreements has not expired.

Yes the statute of limitations can be used as a defense. The Plaintiff must prove its claim against the facts you deny.

Many debt collection defense attorneys give free consultations. Use the Avvo search tool to find an attorney. https://www.avvo.com/find-a-lawyer

You can. But do not ignore the summons. Note, You must respond in the legal way and on time with, for example a motion or an answer with...

Anyone can press charges and the police do not determine who is right or wrong. That is the judge or jury. Consult with experienced attorneys.

Look into a motion to set aside the judgment for failure to lawfully serve the lawsuit.

No. They cannot sue and they cannot pursue Social Security.

Look into any appeal or review rights you may have.

It may be she needs to hire a new attorney. Consult with and hire another attorney before firing your current attorney.

The State Bar may have that information or write a letter to the attorney’s office.