If Missy does return in the finale it would make sense. Last year it was revealed she brought Clara and the Doctor together. If she was the reason they part it would bring it full circle and give Doctor yet another reason to hate her. 
Missy doesn't have to kill Clara directly although she could easily if she wanted too.
Remember what she did to poor Osgood when the Doctor offered to take her traveling?.
Miss can be jealous of others around her "boy friend ". She believes the Doctor still cares about her even loves her.
It could be as a consequence of something she does. Clara is so shocked and traumatised she has to walk away from the Doctor and Tardis. This time for good.
Lots of possibilities. Including using Danny's memory Clara's love for him. Would Clara even consider taking her own life to be with him again ?.
Know it is suppose to be a family programme and watched by young children.
However Clara wouldn't be the first companion to die for love. River did to save 10. Amy let a weeping angel touch her so she could be with Rory in life and death.
Technically the tragedy in New York was a murder/suicide.
Whatever happens it will be sad when she does leave. Although it will give us a chance to get to know a new companion.


Missy doesn't have to kill Clara directly although she could easily if she wanted too.
Remember what she did to poor Osgood when the Doctor offered to take her traveling?.
Miss can be jealous of others around her "boy friend ". She believes the Doctor still cares about her even loves her. It could be as a consequence of something she does. Clara is so shocked and traumatised she has to walk away from the Doctor and Tardis. This time for good.
Lots of possibilities. Including using Danny's memory Clara's love for him. Would Clara even consider taking her own life to be with him again ?.

Know it is suppose to be a family programme and watched by young children.
However Clara wouldn't be the first companion to die for love. River did to save 10. Amy let a weeping angel touch her so she could be with Rory in life and death.
Technically the tragedy in New York was a murder/suicide.
Whatever happens it will be sad when she does leave. Although it will give us a chance to get to know a new companion.

