Wow! Only two months into the relationship, and she`s already starting to gripe about where you spend your time...but yet, its ok for her to cancel the plans because of a friend? I would remind her that your job requires you to be gone half of the month, and if she don`t think she can handle that, then she needs to let you know now, before you waste anymore of your time with her.
It doesn`t sound like she`s a very...give and take type of person.
If you see her in your future, then you need to let her know how you feel, and hopefully, she will understand, and be more patient...if not?