What kind of wedding ring should I buy for my girlfriend?

Unless your and your girl friend’s customs are different from the
customs I know, the couple generally chooses the wedding bands
together – it is a joint decision.

Personally I like the type that is an intertwined engagement ring
and wedding ring set. She can wear either separately, or link them
and wear them together as if they were one.

But there are many different types of these also.