Hi all
I think you should advise your daughter of the health risks with having peircings, but I would also advise not to come down too strongly on her. I feel that if I was given the responsibility to make my own adult, thought out decisions I probably wouldn't have had the peircings I did.
By 17 I had my tongue, nippple, belly button (3 times), nose and ears peirced, and had a tattoo. I particularly regret the tatto but because I was literally banned from leaving the house I guess it was a subconscious rebellion thing. If I was given the choice and the facts I probably would have given myself more time and made a more mature decision. Also, if your daughter is likely to do this surely it is better you accompany her to a reputable place than her go with a gaggle of friends to a backstreet joint?
I personally don't think a tongue peircing is too bad; any peircing involes a risk, but a tongue can be hidden (I wore a small silver stud to work and nobody really knew it was peirced).
Perhaps you could compromise, say in 4 weeks if you still feel the same and have shown that she has researched it herself and promises to keep smaller studs in when at school/ college / work/ nan's house then she is free to wear more decorative ones when out with friends?