How to babysit a baby with separation anxiety and what should I do??
Have her dad play peek-a-boo with her there, where he hides behind his hands and then shows his face again. Then after a few minutes, have him hide behind the doorframe and pop out continually, like "Here I am! Now I'm gone! Here I am!' Then have him make the periods he goes a little longer and a little longer. Over time, she'll get used to the idea that he goes away and comes back. This might require several sessions. You can also try playing with her while he's in the room, so she can see that he's nearby but that her focus is on you. And it's okay to say "This doesn't seem to be working, what do you think?"
Lessen how to calm it down by building a Relation with the kid. Read to it, play with It, walk it around outside, bring it toys to Play with. Build up your social skills. Make Funny faces with it. Etc etc
Give him freedom and let all be as it is. May all have freedom and truth.