It's An IUD, Not An IED

My girlfriend and I have had a sexual relationship for quite some time now. At first she was taking the pill so I wasn't concerned. But then I noticed that her prescriptions were lasting much longer than than they were designated for. She must be forgetting the pill sometimes. I told her about how risky it was to forget the pill and she basically ignored me. I am scared to have sex with her knowing she cuts corners on BC.

My solution: IUD. It's more effective and easier to use than the pill, and safer too. Her health insurance pays for it so I don't understand why she's reluctant. But every time I bring it up she FLIPS OUT. Why?? IUD is more than 99% effective compared to the pill and condoms which are like 80% effective when used imperfectly. What's the big deal?