A man escapes from jail with the help of his girlfriend.
• Four girls are accused of being the man's girlfriend.
• His girlfriend is lying.
• Two girls are innocent and telling the truth.
• The other girl is the man's sister who is helping the girlfriend lie.

The statements of the four female suspects are as follows:

• Anne: "Megan is his girlfriend".
• Emily: "Anne is lying".
• Viola: "Emily is lying".
• Megan: "Viola is not his sister".

Determine the name of the man's sister from the above mentioned clues. Who is his girlfriend?