Lily+Snape=Lala

What if before getting together with James Potter, Lily Evans and Severus Snape had a brief affair? What if the ending of this affair was
because one drunken night and a shot gun marriage, between Lily and
James. What if Lily thought that drunken night ended with her and James making a kid, when really it was Lily's and Severus?

Not wanting to break Severus's heart that she cheated on him AND
was gonna have his enemies child Lily ends it. It's not 'till Lily has the kid does Lily realize her error. The little girl is undeniably Severus's kid. What will Lily do? And to make matters worst Lily stages her daughters 'death' and James trying to consol Lily, which leads to ... Harry.

Lily is stuck. She doesn't want to hurt her son and James because she loves them just as much as her daughter and Severus. The day of
Lily's death and explain what happened to Severus but... as you
know died. What happens to Little
Snape Evans? Will Severus ever find out about his kid? And where was Snape Evans when she was 'dead'?