My sister has started to hallucinate.What do I do?

My sister has been fighting a chest infection for awhile now.2days ago she started seeing people n bugs that was not there.she becomes very upset and thinks im trying to put her away.I only want to help her cuz this is my sister.the people wont talk they just wont leave when she tells them.could this be from the infection? is it going to her brain or in herblood stream? i dont know what to do!!!