My sister and I are both nulligravidas and both have IUSes. She has Mirena and I have Fibroplant. We've both had Mirena and Fibroplant in the past and I'va also had Flexi-T 300.
My and my sister both struggled with the frame size with Mirena the first time, with cramping during and between periods. The insertion pain is off the scale, screaming levels of pain. When I went to the late Dr Wildermeersch for my first Fibroplant, he did something no other coil fitter had done before. He gave me cervical anaesthetic. Local anaesthesia during a coil fit is a game changer: ask for it!
The Flexi-T 300 was bearable without anaesthesia but not pleasant. It was nowhere near as bad as the Mirena and it's one of the IUDs recommended for nulligs.
Why don't my sister and I just take the pill or a hormonal LARC? Dsis was hospitalised with a blood clot in her lungs caused by the interaction between the oestrogen in her patch and an, at the time, undiagnosed clotting disorder. You don't know what you and your DDs are undiagnosed with, is it worth that risk? I was banned from the pill aged 20 when NICE decided that quadrupling women's risk of stroke was only OK if they didn't have migraines. My sister and I both become depressed on progestogen-based contraceptives. I went on depo provera in my early twenties, I wish I'd never let that needle near my body because I gained three stones in nine months and started self-harming, and I've never lost more than half of that weight since.
The complications I mention above are not as rare as you might think. Weight gain on depo provera is well-known, as is depression.
So, OP: encourage your DD to get a Flexi-T 300 and ask if the clinic can use cervical anaesthetic. You are entirely reasonable in wanting her to avoid the adverse side-effects of hormonal contraceptives.
And tell her to use condoms anyway, she doesn't know where her boyfriend's been not who he's been there with.