My companion got into my power armour when I exited to use a cooking station, how do I get her out?

Bring up the command wheel and select talk. There should be an option that is "Exit Power Armor" or something like that.

Correct, and if you for some reason want to put your companion in a pa on purpose, just use the command prompt, aim at a empty pa with a core and you should get the option to tell them to enter it.

Worst case scenario pickpocket the fusion core out and it will eject them, this works for anyone who steals your armor.