You cannot gaurantee what is going to come up in paper 1, you can be sure that once paper 1 is known, all the other types will appear in the second paper [plus 2 unknown cossovers and Zs again.]
The split between the 2 papers will change every year. There are 12 types on paper 1 with the other 9 [plus Z plus 2 crossovers] on paper 2. The 12 will vary every year as will the 9.
One year paper 1 may be C, L, G, I , D, M, S, O, A, J, F and Z
Paper 2 may be N, U, K, P, B, H, Q, R, E with crossovers of Z, S and F
The next year , paper 1 could be C, N ,K, G, R, E, Q, D, B, A, J and Z
Paper 2 may be L, U, P, I, O , H, F , M, S with crssovers Z, Q and C
So, although the 21 will appear over the 2 tests, the mix will change each year as will the crossovers.[except that Z appears in both tests]
So no you cannot assume she has a fair chance of passing 1 paper as the mix will vary. Best to make sure she is confident in all areas.