How blood type O would have killed her if she's B ?
The doctor said they had to be sure of group because group 0 could kill her if she's B...
But B can accept O...
Problem was with rhesus...
If she was type B+ there probably wouldn't have been a problem with O+ or O- provided she didn't very large quanities of it. If she was B- on the other hand and the blood was O+, then she could have a reaction to it. The doctor was right to check and make sure of the types.