Crucial Support of Girlfriend Puzzle : Solution

What was the puzzle?

What we know so far.

A man escapes from jail with help from 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. 

And statements of four girls are - 

Amanda: "Melinda is his girlfriend."

Vanessa: "Eva is lying."

Eva: "Amanda is lying."

Melinda: "Vanessa is not his sister."

Now, for a moment, let's assume Amanda is telling the truth. Then Melinda must be man's girlfriend who is lying. Therefore, Vanessa must be man's sister who is lying in support of man's girlfriend Melinda. 

So, Vanessa's lying statement suggests that Eva must be telling the truth. But as per Eva, Amanda is lying which is contrary to our initial assumption that Amanda is telling the truth.

So, Amanda must be lying.

If Amanda is lying then Eva must be telling the truth. And if Eva is telling the truth then Vanessa must be lying. 

With that we have 2 lying girls viz. Amanda and Vanessa & Eva as innocent girl telling the truth. Therefore, other innocent girl must be Melinda who must be telling the truth. 

So, as per innocent Melinda, Vanessa isn't a man's sister, hence Amanda must be. And Vanessa is man's girlfriend.