sorry to break the bad news but u r doomed in this case. Every "service" of that kind in europe requieres and "sms text message" approval. That means in order to track the phone (has to have gps) , to send the text and then the other person has to confirm that she wants to be tracked , very poplular service in my country to track your kids (in this case you program it yourself)

2. scenerio is go to her parents and ask for the papers to the phone (samsung s5 like u said) and find the emei number , once you get that  PM me .
You provide me with the last 4 digits of the emei and if its compatible with my program then i can track the phone in 5min .