How do I track a GPS device that has no connectivity with an internet or cellular network? Are there any GPS devices that can be tracked in real-time WITHOUT the use of a SIM card ?
Or is there any possibility to track a GPS device which has lost the network signal ?
Assuming they can both send and receive sms and mine has internet connection ?
Something like every minute it checks, not need for a real time hard track but as good to know where to find her if she gets attacked.
I want to develop an app for it
That's a little confusing: No SIM = no SMS. No network = no connection = no communication. GPS is only a receiver, it does not send. That leaves binoculars as only tracking method then – which, besides, even works with devices not featuring GPS. As long as visual contact is possible, at least ;)

Apart from that, I guess we've got an XY problem here: "good to know where to find her if she gets attacked" › How do you know she's attacked? GPS alone won't tell you.

Maybe you're rather after Personal Protection solutions. There are some featuring an "emergency button" – and others with a "dead man's switch": the former sends out an alert when pushed, the latter sends one if not pushed within a given interval. If such an app is good, it figures what means of communication is available – and can broadcast an distress signal by all of them: Sending out SMS and mails including the coordinates (GPS or network based, whatever is available), posting on Twitter/Facebook, and even initiating calls to 911 (or whatever number you tell it to use).

One such app would be Watch Over Me, including most of those features: Track-Me function, Dead-Man-Switch; Real-Time recording; Email/Facebook, and more (on subscription even more again). For alternatives, simply follow the link to my list :)