She can absolutely
not stay with you for the term of your assignment. I'm sure you know that Portugal and Switzerland are two different countries.
She can stay 3 months then she must leave for three months.
Generally you need to be married for her to get a visa to stay with you. But you can try and ask at the commune if you can sponsor her stay. They
may allow it. Generally they don't. But in some instances they have approved if you can show you have enough money to sponsor her stay.