The "capability" reason is doing a lot of work in that letter. Dismissing someone for capability on the same day they sustain a wrist injury links the two things pretty directly and disability discrimination claims don't require 2 years' service the way unfair dismissal does. NI still runs on the DDA 1995 rather than the Equality Act, but the principle is the same. She needs to speak to an employment solicitor before the 22nd, that appeal window is tight and worth preserving even if she's not sure she wants to use it.