Damned if you do, damned if you don't
Sounds to me like the MoD was buggered either way.
They moved her for what they thought were the correct reasons (operational service when preggers, reduced standard of ante-natal care etc).
If they hadn't removed her and something went wrong with her pregnancy, she may well have sued for even more.
She was lucky enough that she got a posting with her husband in the first place, many more service people don't (not saying it shouldn't happen, but just that she should be grateful for it).
As for missing out on promotion because she was on leave and didn't receive a performance review 2 things spring to mind.
1. Why is it so difficult in this day and age to sort out the review irrespective of where you happen to be?
2. Even if she had the review, was she 100% guaranteed promotion or was it just that she missed out on possible promotion?