Consider things from her perspective. What part of being a military wife (or girlfriend in this case) sounds appealing? Your partner never being home? The only communication being like skypeing 10 minutes a week? The constant fear that if your partner is deployed somewhere dangerous they might never come back? I'm sure you have your reasons for wanting to join the services, but you need to weigh that against your girlfriends concerns. It ultimately is a matter of whether you care more about how you feel, or you care more about how she feels.