First of all she's 12 years old. Ok so this might be wrong in some peoples eyes and I personally don't do this but I've been told I should track my daughters apps like Snapchat for example.

But I've been told Snapchat can't be tracked.

If I put her on my family plan is there any possible way I can see what she writes or shares on Snapchat even though the stuff erases after you close the app?

Right now she's on her own phone plan.

Is there any possible way or like an app I can download to see what she does?

This is targeting more towards SNAPCHAT obviously LoL because it's the only one I know of that deletes info after a closing the conversation.