I'm sorry but are you here to vent and gain sympathy or to inform others?
For those on this site recruiting, let's use the above as an example for how not to prepare for consulting :)
1) It sounds like you view yourself as the centre of the universe, which, if you want to work in a high-stakes place like McKinsey, is an attitude you need to drop!
2) You shouldn't be judging a company based on just one person (perhaps she is really bad, I wasn't there, but this one situation should not put you off from such a reputable company). This is anectodal...you need to look at the facts/the whole
3) You are not her top priority - she will be getting dozens of emails DAILY from candidates desperate to be invited in. You accomodate her, not the other way around. As you would have to do for Partners, Clients, etc.
4) Not sure you should complain about her typos given the text above (specialy, didnt, "I ended up on my nerves", whych)
5) I think it's a problem that her simply not including a time got on your nerves - I fear for your first client interaction
6) It sounds like you didn't do the research about what roles work for you before speaking to her. She's not there to baby walk you through the process
In summary, to thrive during recruiting, interviewing, and on the job:
1) Count yourself lucky to be there
2) Look at a problem based on the whole, not small anecdotes
3) Put others before yourself
4) Have attention to detail (typos on final slides will kill you)
5) Brush off the little (and the big) things - always keep your cool, especially with clients
6) Drive your own case/project forward and do your own research...you own your own module