mine has been frustrated with the situation that we were stuck in, and that she couldn't help out more. that is what she said, but i think she was also frustrated at me--how could you not?
i could see her getting mad if i showed up drunk or otherwise intoxicated or told her about something stupid i did that was working on sabotaging our therapy.
on the other end of things, my T recently told me that i am allowed to show anger in there, and towards her!!!

YEAH RIGHT, T! I told her i couldn't even imagine doing that, and she goes, "Well when it happens, we know progress will have been made"
Another time i was talking about how i can sometimes feel uncomfortable around opening gifts with family--because some family members give me some AWFUL gifts, and i just have to fake it that i love it. my T goes "well if you got a gift in here (theoretically), you can totally tell me you hate it!" and she said it with such happiness in her face.