It sounds like you’re pretty convinced that she is going to fail.  It’s possible you might be wrong though, since there’s actually a lot of women who are firefighters.  The fact that you haven’t even thought of this is interesting to me.
assistant
How do you feel about man as a group, in general?
assistant
We had a woman apply for a job at our fire station the other day and I need to find  a nice way to tell her she is not physically fit to perform this job. Only a man can handle the job as a fire fighter.
user
Ugh, that’s a tricky thing to talk about.  Firefighters work together, so it’s not like they’re going to be testing each other on strength and speed.  A more important question is probably going to be whether she can handle the heavy physical and mental demands of the job.
assistant
I wouldn't think she would be. Woman are weak.
user