General Discussion

She's there to calm him down and gatekeep his interactions with others, ensuring he is in the right mood to be able to receive visitors, and is properly prepped for any news they might be bringing. Her administrative duties are pretty much deciding what business paperwork goes to him and what can doled out to the proxies; while she might have some power, she doesn't appear to have the normal responsibilities a Chief of Staff typically exercises.
Seriously, she appears to act more as a 1950's/1960's executive secretary with some administrative signature power.
On edit - she's not there to be his Chief of Staff, so it's rather difficult to say she's incompetent. Especially, since that isn't what she's there to be. She just was given the title as a reason to have her there.