Glinda was a pot stirrer....

Think about it. The witch wouldn't want anything to do with Dorothy had Glinda not made it obvious that it was Dorothy's house that fell on her sister. Glinda was the one who put the Ruby Slippers on Dorothy's feet (pissing off the Wicked Witch). Then she sends Dorothy out on a wild goose chase into a land she's unfamiliar with to find the Wizard. During this whole story line, she knew Dorothy could've gone home almost as soon as she got to OZ with the slippers.....what a bitch.