What if she decided to walk when she found out she was going to be evicted? Maybe she just thought "F BB" and went out the back door.
Obviously BB cannot say that is why because it would reveal she knows about her eviction, so they just say she is ill and has immunity.
Then tomorrow they will say she has retired from the show due to injury?
That would explain why none of the housemates seemed worried at any point during any part of the footage we seen from uploads and show.
If she freaked out and told everyone what she thought of them that could be considered an illness, if she lost the plot?