Alex escaped prison and his girlfriend assisted him in the prison break. A detective agent was appointed don he case as Alex was an elite class criminal. The detective circled down on to four girls and took their statement:
Megan - 'Maggie is his girlfriend.'
Charlize - 'Katie is lying.'
Katie - 'Megan is lying.'
Maggie - Charlize is not his sister.'
Now, the detective knows that out of these four girls, one is Alex's girlfriend for sure and one is his sister who is assisting his girlfriend in lying. The other two girls are innocent and are speaking the truth.
Who do you think is Alex's sister?