I have to say that whilst I would not have told the parents, I would have cautioned the pupil that I couldn't keep this confidential, and would have then seen the HoY, or the child protection teacher as IMO this is a child protection issue, and teachers HAVE to cover their own arses unfortunately. It is not about the 'rights' of the 14 yo to privacy but about the law and teachers are judged and disciplined by how we act in accordance with the law.
On the other hand, I have bought a pregnancy testing kit for one of my year 13s and kept quiet about it, but she knew what she was doing, as she was 18. I still gave her a chat about using contraception, STDs and why 28 condoms are always better than 1.
This also highlights why there should be teachers or personnel in schools who deal solely with pastoral issues, and receive the appropriate training to do so. I always felt very uncomfortable dealing with issues like this, as we don't receive proper training in these areas; we are TEACHERS, not social or youth workers. I can deal with most things that the pastoral role throws up, but things like this where it is pretty clearly defined what your legal obligations are, have the potential to develop into a minefield as is so clearly displayed here.
YANBU to be indignant that your friend is being disciplined, but YABU to think that she was right to tell the parents..she should have gone to the child protection member of staff, or the HoY, and should NOT have promised confidentiality.