Employee and spouse attend an off site Company meeting. Can the cost of the spouses meals be a taxable benefit to the employee?

Was she required to come ?

First, the employer myst REQUIRE that the spouse be there, and provide written proof of that requirement.

Even then, the IRS will be extremely skeptical of the deduction, because most employers would pay tge wife's expenses if they needed her to be there.

Bottom line, the answer is no.