from collections import defaultdict

tests_dict = {'test 1': ['Manuel', 'Mariana', 'Filipa'], 'test 2': ['Manuel', 'Filipa', 'Mariana'], 'test 3': ['Mariana', 'Manuel', 'Filipa']}
peps_dict = defaultdict(dict)
for test in tests_dict:
    for indx, name in enumerate(tests_dict[test], 1):
        peps_dict[name][test] = indx
print(peps_dict)