What was the name of a movie about demons trying to attack girl that is pregnant and angel defends her from diner?

You're likely thinking of the 1994 movie "The Prophecy".

Here's why:

* Demons attacking a pregnant woman: The film features a pregnant woman named Mary, who is targeted by demons.

* Angel defending her: A fallen angel named Gabriel (played by Christopher Walken) is sent to protect Mary.

* Diner scene: While not the main location, there is a scene in a diner where the demons confront Mary.

Let me know if this is the movie you were thinking of!