It is all Coras fault! As anda all said, snow was just an innocent little girl that wanted Regina to be happy but got manipulated oleh that WITCH!!!
Regina should blame Cora! NOT Snow! As Lana berkata Regina was thinking: " anda little, selfish BRAT! anda just wanted me to be your stepmother! anda don't care about ME being happy!" Thats what Lana berkata Regina was thinking at the time when she was getting dressed for the wedding. But we don't know why Regina went 'Extreme Power-Mad' yet....she went WAY extreme to rid Snow! But...she didn't know any different....
Someday in season 2/3 I want to see Regina confront Cora and apologise to
Snow somehow and get 'redeemed.'