My parents were likewise bothered when I got my first tattoo at 18. Some 24 years later, I'm still fond of that tattoo. It's nothing short of arrogance to assume that your daughter will regret it later. She might come to cherish it even more.
Anyway, she has a shamrock with flowers across her lower back, and she just got started on a double tattoo on both sides, about 3 or 4 hibiscus flowers. Mind you, she's 5'3" and weighs about 108, just a little thing, and I really think she's not taking her size into account when she designs these images.
For the record, I allowed her to get the first tattoo last summer (she was only 17) because it was Irish, but it quickly evolved from a little shamrock into an ornate one, which was a surprise. Now I think she's going overboard, but there's nothing I can really do at this point.