In this context "she is blunt/direct/unnafected/pragmatic/unsentimental" etc.
That is, she says what she thinks frankly/directly without falling in emotional traps, in an energic way.
Nothing will have an adverse influence in her emotional balance, if she feels she is right.
It´s no use you shouting, to lie, go crying, slam the door, throw a tamtrum, snap at her, swear falsely, threaten her with words, whatever you have. She won´t change her argument, and all that won´t convince her of your point, it can only make matters worse. Ha ha ha.
What a definition!
Matter-of-fact can be all these, in some given different contexts...http://thesaurus.com/browse/matter-of-fact