Option 1 - daughter sits paper, does as well/better than expected
Outcome - grade on CV 9/8/7/6/5/4; grade reported on school tables 9/8/7/6/5/4 (grades 9-7 roughly old A/A*, grade 6 top end of B, grade 5 lower B/top C, grade 4 lower C)
Option 2 - daughter sits higher paper, does poorly
Outcome - grade on CV and on school results U
Option 3 - daughter does foundation tier (easier questions overall, some overlap with higher paper), does as well or better than expected
Outcome - grade on CV 5/4; grade (reported on the same table as above!) 5/4.
If she gets a 5 or a 4 on either paper it will look the same on the results tables for the school and her CV (unlike CSE/O level)
If she attempts the higher and is panicked by harder questions she could end up with a U if she doesn't reach the 4. (This will be recorded on the tables.)
If she does the foundation she will have easier questions (although will need to get more right to get a 5/4), and the safety net of the rest of the grades before a U. (This result will also be recorded in the same tables.)
It is in the school's interests for your daughter to get as high a grade as possible. The results of the foundation and higher paper will be recorded together.