I'll take a shot at this question as I will always try to answer ghost questions!
I wouldn't say that a ghost would be immediately be booted out, its mentioned that a nuit is a body switching creature right? Its life essence along with its soul is transferred into a host body until it decays: that body essentially becomes the nuits! A kind of shell for their soul... Now a ghost can posses anything that has a soul, life essence (Djed) with the exception of the Gods themselves and undead capable of becoming ethereal. A regular nuit facing possession wouldn't be any different from a human or an animals facing spiritual intrusion, they'll notice that ''booting'' wouldn't immediately occur and the spirit especially one that is violent would put up resistance.
Novice Possession Vs Sheer Willpower= Willpower Instant Win!
A weak ghost unfamiliar with possession but is attempting to possess an individual would face some issues with their target... A novice ghost would have to take advantage of its victims mental state and take into consideration just how strong the will of its victim is.
Err... A possession skill I believe lower than 10pts would cause the ghost to loss the internal conflict/struggle and thus fail in its possession, exhausting it and its victim.
Hoped that helped some!