Without knowing the people in question, it's possible that the person sending the email has something of a point.
But it is an absolutely horrible way of dealing with the situation.
If the teammate really isn't ready to do her first crit, then her teammates should work with her to address any unsafe riding, and help her improve her skills. If the team really thinks the person is dangerous, and not willing to learn, then they don't have to be her teammate.
You don't go around throwing your teammate under the bus. I bet that email will haunt its author for a good while.
__________________
You could fall off a cliff and die.
You could get lost and die.
You could hit a tree and die.
OR YOU COULD STAY HOME AND FALL OFF THE COUCH AND DIE.