I think it's mostly  the vaccines used on the girl were probably expired ones

OR

1. she started the course late . Incubation period is usually 2 to 3 months or even longer depending on the bite location. Course is usually 4 injections-1 every week, so about one month long.

2. the vaccines were not stored properly- but what are the odds of all 5 doses being incorrectly stored as well as the immunogoblin injections

3. This case must be thoroughly investigated