I didn't know women still used a shield. That means her boyfriend isn't using condoms exposing her to diseases.
When IUDs were first introduced they were really hyped despite alot of side effects. They didn't totally disappear, and have made a comeback with some supposedly new "improved" versions. Don't confuse the IUD with cervical caps, diaphrams or "female condoms" (which all act by creating a barrier).
IUDs still have alot of dangerous side effects, despite claims of being safe.