Visa to sweden

Hi everybody!
My girlfriend from Vietnam is coming to see me.
she is planing to stay for 3 moth
what type of visa is the best to choose?
what else is important to think of.
she is staying with me and I cover all her expenses
and ofcourse make an invitatio to  her.

It looks like if your girlfriend is from Vietnam she needs visa. You should read this page where you see how to achieve a visa https://www.migrationsverket.se/English/Startpage.html
If you'll find it difficult then do not hesitate contacting them. read more on https://www.migrationsverket.se/English/Contact-us.html