adding new boxer to family?

Question
I have a 6yr old female (spayed) Lab and a 2yr old male Boxer.  I am considering adopting  another Boxer, female-2yr old who needs a new home.  My question is whether or not I should expect issues between the two females.  (I have a friend who is discouraging me from adopting the new dog because the two females "will have to establish a pecking order".)

Answer
If you know any history about the 2 yr old female Boxer that you are considering adopting, it will help you a lot.

Females can be, but not necessarily, competitive.

Is there any way you can bring her into your home on a trial run to introduce them all?

If so, I suggest you get help, and leash the two females, and allow them to smell one another and do the "dog" greeting thing, and see if there is any aggression of either. Do this a few times, and if all goes well, unleash them, with help around, and supervise them to see their compatibility.