Why many of us don't want to leave their comfort zones?

I just arrived home tonight and saw my housemate who recently got dumped by her boyfriend!

me: Hi F.
F: hi, with a frown face!
me: you seems not too happy!?
F.: no, I hate my work.
me: Would you like to talk about it?
F.: No!
This was the conversation we had. What always makes me wonder, this is the 4 times I hear this statement from her that she doesn't like her job at the university.
I begin to think:
Why she doesn't try something different?
She does go to painting and performing classes, but she complains the classes are too hard! She has to memorize tons of scripts for the theater class! The teacher takes it too serious!

Why people in general hate to leave their comfort zones?

She is not married, doesn't have a child, what is she afraid of? what are we afraid of?

She needs a boyfriend, a partner? I understand...
She is a women, all she need to do have to meet people, talk to them and be truthful
to herself and them! why she doesn't do it?!

I told her a few days ago when she felt down and talked about the last boyfriend; why don't change the way you meet people, perhaps internet!

" I hate that way, to meet people", she said.

I wonder if someone is so stiff, it makes it even more difficult to find someone. From a mathematical point of view, a stiff differential equation may create lots of high frequency noise!!:-)

All and all, she may be just having a PMS! who knows!