So how come the OP's update didn't include how the police warned the 12 year old that she may face prosecution? After all, its legal fact. Seems there will be rather a lot of disappointed posters who were only saying.
Whether or not the police decide to make the point to a young girl who is the victim of grooming doesn't determine if a crime is a crime or not
She's. Not. Going. To. Face. Prosecution.
They may have decided that it wasn't the time to bring it up. They may not bring it up at all. That doesn't mean that a criminal act wasn't committed according to the legislation. That's not how law works.
Under different circumstances then sending explicit photos would be illegal, but the fact she's been groomed makes all the difference.
Again, that's not how the law works. If you can find the part of the Act that lists being the victim of grooming as a defence then I'll gladly admit to being mistaken. But unless that's in there, it isn't a defence. The police don't get to just ignore the law and decide whether a crime is a crime because of the horrible circumstances surrounding it. They can only decide whether to pursue it or not. Which they won't, because it would be ridiculous to treat her as a criminal, and isn't in the spirit of what the law is intending to do. That's the discretion they have.
Incidentally, for those who were only pointing out the facts, maybe the person who solicited these images might have explained the law to victims as well - co-erced them into it and then said "you know you can be prosecuted don't you? Only saying".
All the more reason for parents to be more widely aware of the actual law, and how it is handled by the police and social services in practice, surely.