What happens when I take the librarian into my household ?

I am playing as a male sim, he does not have a computer yet so he often goes to use a computer in the library in Winddenburg. I don't know why every time the librarian meets him she suddenly gets the flirty mood. My sim does not have any romance related trait, he has the Neat, Love Outdoor and Good traits. He is still single so i think if the librarian likes him so much, why not build a relationship and marry in the future. But my questions are:

1. If he marries the librarian or gets her to move in, will she still have the same job ?

2. If the answer to 1 is yes, will I see her on duty at the library when he visits the library ?  

3. If the answer to 2 is yes, will i still be able to control her while she is on duty at the library ? 

4. Do the answers to 1 - 3 apply to other careers of NPCs ? Such as the DJs, Bartenders ? 

Forgive my English if any error.