From a purely employment perspective, I would recommend downplaying the "girlfriend" aspect of the move. While moving for family reasons is a perfectly suitable reasons for relocating, the term 'girlfriend' implies a sense of immaturity in the relationship, that 'fiance' or 'wife' wouldn't. First of all, I'd recommend using the term 'partner' when speaking about your girlfriend as purely terminologically it hints more towards stability than 'girlfriend'.
Furthermore, look at this from an employers perspective, regardless of your commitment to your relationship, when you say:
I am looking to move to Newtown to be with my girlfriend who is studying at Newtown University.
A few questions spring to mind:
- How stable is this relationship?
- If it goes sour will the applicant have a good enough support network to manage a break-up and working in a new environment?
- Will the applicant stay in Newtown if something goes wrong?
While not all of these may be consciously thought or spoken about, these are the kinds of instability that might tip an employer in one direction or another.
What I'd recommend, is learning about the city/country you are moving to, and building a few other reasons for moving that you can speak about. Are there renowned professional communities in the area? No-one would question a technical person moving to Silicon Valley or an arts person moving to New York, even if they had the same motives as you. This also helps demonstrate a wider support network that would help in transitioning to a new city.
Also, if the country has a large community of speaks in your non-native tongue, you could also use this. For example, moving from the United States to Europe to practise or learn a new language.
This way if asked, you can honestly answer, like:
I am looking to move to Newtown to be with my partner who is studying at Newtown University. However, I've always been interested in programmer community in Newtown, and am hoping to improve my Esperanto.
By giving other reasons that attract you to the town you can help might allay any concerns of stability and risk the prospective employer might have about taking on an employee who would be moving a great distance.