Snape's love interest

[theadimail]

No: HPFGUIDX 139773

There has been lot of speculation that Snape's love interest was Lily. 
Though this  looks unlikely after the pensieve scene in Book5, many 
people have either taken it for granted or simply have not taken any 
stand on the matter. It is one of the least argued points in the 
cannon.
 I think however that Snape's love interest is Narcissa Malfoy. It is 
his love for her that prompted Snape to make the Unbreakable Vow. I 
also think that Narcissa is aware of the fact and that is why, she 
turned to Snape for help in the first place. 
  How does the theory sound?
Regards,
Adi