I feel like my girlfriend is gonna leave me.?

Me and my girlfriend have been together a year we share so much together, but sometimes she can do things or say things/ not say them at all "I love you" . lke for a example when i was in oregon visiting my family she wanted to go to my frends party but this frend tried to take her from me when i left for oregon the first time, we talked about it i said i didnt want her to go and she flipped at me like she ddnt care what i thought she was mad. She now hangs out wth this guy alot she claims he is her best guy friend and he claims she is her best non dateng GF. he takes her to college everyday she actualy has a cl wth him. and this friend trets me llike **** on the ocasion. now she wants me to take all her stuff out of my house, I now have to say i love you first and she will say it back but she will say it like she doesnt mean it in a snobby tone, I am joining the Marine corps, her father is a LTCOL in the corps and i have recently talked to her father about getting marred to his daughter but now i feel like she is sliping from me. please help......