If she was vaccinated and still caught Covid within a few months of vaccination (immunity wears off in a few months), she may have an impaired immune system.
A person with an impaired immune system only has herd immunity to protect them. Herd immunity works by decreasing the number of sick people who can spread disease. It does not keep a person from getting sick if exposed.
My son got Covid after being vaccinated. It was a mild illness, with some sniffling. Without the immunity in place from the vaccines, he could have become very sick. Hubby and I did not catch Covid, despite this known exposure. We’re both vaccinated.
It ain’t a vaccination. It is some kind of bizzare experimental shot.