Looking for a spy app for iphone 4?

I keep doin web searches I need an app to monitor my 13 yo cause I've done read some letters she wrote n she knows too much already I need one not over $5 but will let me see what she's texting ect I put restrictions on but I still don't want nasty texts n pics from or to her friends w/o me knowing so I can then take care of it I looked up in iTunes Store but games is all that shows names of them is all I need so I can download it to her phone thanks in advance

There's no way to track the messages she sends and receive by app, especially if they're SMS or MMS. They are designed to be a direct sender-to-receiver process (unless theoretically interpolated during the send process) that can't be tracked.

If your 13 year-old is using some secondary messaging service, like Kik, Facebook Messenger, iMessage, etc, then you can make an agreement to log in to the same messenger service on your device to see what your child is sending and receiving. But if it's SMS/MMS, then you don't really have much to control.

The phone carrier may help you with their own services since they handle the information exchange, but in terms of using something direct and instant, you don't have much options besides not giving the child a phone in the first place.

Some phone carriers provide a service where messages can be sent to a hidden "second sender" (kind of like Blind Carbon Copy (BCC) in email), or a forwarding service where any received text is forwarded to your phone. Again, this is as much as you can do with tracking. Controlling it isn't much of an option.