Drubsa is right. I never really thought about this before so I looked it up.
The lowest level of Forgery in New York State is defined as "with intent to defraud, deceive, or injure another, he falsely makes, completes or alters a written instrument."
"Falsely make" and "falsely complete" have there own definitions but they involved doing something without proper authorization.
There is no intent to defraud, deceive, or injure another and Simba's Mom's husband authorized her to sign his name. That means there is no crime. I also doubt there is any title defect.
I have never forged/signed my wife's name and probably never will.