My advice: Long distance relaitonships are hard, and joining the army will make your relationship a long distance one
LDR's aren't impossible, but it just means she has to be really worth it and you have to be really worth it to her for it to work.
Also, before you get into a relationship with her, make sure she understands you'll be leaving to the army, she's had heartbreak before so no need to spring it on her as a surprise.