Airforce job and argument between 2 teenagers?

My son is 18 and works as police in airforce. he wants 2 marry 18yr girl here when he comes back from korea. he talks 2 her everyday and as a teenager she nags about everything.leavin him stressed bout her and doing his job.he wants me 2 talk 2 her which i never hav. i think she needs 2 understand his stress an talk 2 him les.wat would u say 2 a girl thats a only child in a way she can understand.