For all the posters slating the poster of the 14 year old boy, for him asking is a girl on the other end sending them.
My friends son gets nudes sent from girls his age completely unprompted all the time.
Social media and the use of disappearing chats/pics has allowed teens to erode and push the boundaries of risky sexual behaviour in ways they haven't ever before. Which in alot of ways feels safer to them than it has before because its not in person.
It was the number one issue in my dd school for both boys and girls and according to her principal more of her year were engaging it that weren't, and those were only the times that had been flagged to the school by one of the kids involved getting caught.
Considering snap chat is now used as one of the easiest ways of sexting/porn for adults it doesn't mean teens using it are 'sexaul predators'.
And throwing out words like that makes it easier to move away from the uncomfortable fact that teens are exploring and engaging in sexual activities in ways they weren't 10/15 years ago with blurring of what they consider somewhat safe because it isn't in real life.
They can access pretty much any only fans content creator on reddit for free. Twitter is flooded with sex video clips.
The reality is once you give a teen a phone you no longer have really any control over what they are looking for/texting/watching.
They can by pass parental controls easily. If you stop them having Snapchat, they can use IG DMs or Twitter or WhatsApp.
So to an extent unless you take a phone away from and full Internet access if they want to they will find a way to engage in this behaviour.
It's the exact same as not being able to control if they decide they want to have sex.
At 14 I would ban snap chat, because it is one of the most difficult to police.
Check your Internet safe searching and connect to a family monitoring account.
Do random spot checking on her phone.
Go online and watch some Internet safety videos and watch them with her. Explaining what can happen if she chooses to send nudes or videos. Or shares ones she receives.
Tell her she can always always tell you if she does something or receives something that makes her uncomfortable.