Yes, there is an app that forwards text messages received by a phone to another mobile phone.
It is produced by DLP Mobile and is called "SMS Replicator".
Here's how it works:
Getting your girlfriend's text messages:
- The app runs secretly
- You need to download the program onto her phone
- It gets hidden and runs in the background so she won't notice
- Enter the phone number you want to forward messages to
- You can deactivate it at any time
Now you asked about not touching her phone at all. Well, it may be a little tricky because the app does need to be installed, but you can get HER to install it by attaching the file to another download (look up how to do that exactly, I' not sure.. But I'm 100% certain it can be done).
You'll also need to enter the phone number to forward messages to, but that should be a 3 second job - so just ask for an excuse to check the time or something... It won't take long at all to start receiving all the messages she is getting... And from whoever she is getting them too!