Just have the same to say as everyone else really; a proper tattooist will only tattoo you if you're 18+, anyone who's prepared to do it at 17 I wouldn't trust! When I was 18 I went and got a tiny heart on my toe in Ibiza, it's small enough to cover up easily and it satisfied my 18 year old 'I want a tattoo' without being a massive regret.
Show her this website; failblog.cheezburger.com/ugliesttattoos and encourage her to spend the time until she turns 18 really planning her tattoo and researching proper artists! Tattoos can and do look amazing, but only if people have really done their research before! That website is hilarious and will show her what happens when people don't think before they get inked!!
I'd suggest she wait til 18 as she will be able to get it done at one of the better places, that will demand to see her ID. She could always start on the design now. Having said that, my (resourceful) 16yo has 2 stunning tattoos, one on her ribs & one on her forearm. Both are beautifully done, non generic and rather lovely.
refuse seeker you will only resent giving her permission honestly I did with mine and she didnt get it when she was 18 , If your dd really wants 1 she will wait, I said to mine I wasn't going to be responsible and give permisison for her to do something she might regret, I am not against tattoos but as i said I couldnt have said it was ok when i wasn't ok with it