Crack - Repair or new plaster?

[EmmaFirstTimeBuyer]

This is my first time doing DIY... Most of the plaster in the bedroom seems fine but above the window is quite a hefty crack. Would it be OK to repair or should all plaster be taken off and started again?
Thanks anyone View media item 83774 View media item 83774 View media item 83775

 

[ree]

Perhaps, post pics showing the whole window frame and the whole of that wall?

Carefully examine the angle above the window between the wall and ceiling - look for cracks.

Do you know when the PVC window frames were installed?

Do the frames open and close freely?

Has all the paper on walls and ceiling been removed?

Please go outside and pic the window area and post pic(s) on here.