I agree with a lot that people are writing - your DD is probably picking up on the anxiety the school feels about their results. Most schools try to handle results sensitively - and my feeling is that if children find out how people did it's either through things like awards at assemblies (i.e. a student who achieved NC L6 last year in English & Maths was awarded a prize from the Headmistress for achievement - and to be fair that should be celebrated!) or children find out because people talk about it (other children especially).
My view is this either way DCs win:
if they pass - they're relieved and pleased.
If they don't pass - their new senior school will identify them as someone who will need extra support from the start. At senior school children will have specialist maths, English & Science teachers (etc....) and these teachers will have a lot more subject knowledge than primary teachers and most likely be better able to explain things.
I know it's hard when a child gets wound up about things, but try to persuade her she has nothing to lose and she's done nothing wrong if she doesn't pass. If she's struggling - frankly that's a sign that the school hasn't been working effectively with her.
I suspect the issue is that the teachers are talking about things generally and your DD believes this all applies to her.
Personally pass or fail - tests are useful. They're a point in the process where you can gauge how you're doing - and that's an important process for everybody - your DD, you & her teachers (now & in future). It is just a snapshot and will never totally summarise what your DD can achieve - but it is our only means of determining where she's at as a student right now. Try to encourage her to see it in that light.
Finally - remind her this is nothing. The test she'll really care about is passing her driving test!