She wants to be able to put hot money into her pension fund and for him to get tax relief on it?
Is the world gone mad altogether?
You put money into a pension fund to get tax relief. If you are not paying any tax because you are illegally evading tax, how can you expect tax relief?
Simple answer is "NO"
If he is earning (and declaring for tax) he can claim relief on contributions he makes into his pension.
If she is not earning (officially) then there is no income on which to pension. If she declares an income, then she can contribute out of that income and claim relief.
Stay at home spouses (who do not earn an income) dont have an income to replace when they retire. If the only (official) income into the household is his income, then that is the income on which a pension can be funded.