Yes, yes, and yes

Melania committed verifiable immigration fraud, working while on a tourist visa.
Criminal Prosecution: Visa fraud is a federal offense under 18 U.S.C. § 1546.
Prison Time: Penalties often include up to 10 years in federal prison for a first offense with a Permanent Bar/Inadmissibility.

As it beautifully says in the novel:
“These salesman faces, always waiting for the lucrative deal. These faces who let every meanness be said to them without losing their forced smile, if they still hoped for the signature. These vessels full of guile.”

Arrest Melania too