I'm a tab bit confused about Supernatural season 5 episode 7.?

After Dean turns old, the Witch's girlfriend visit Dean, Sam, and Bobby at their motel. She tells them how to kill her boyfriend, herself and how to reverse the spell. When Bobby asked her why she would give out that information she says, "I have my reasons" and started playing with her necklace. During Sam and the Witch poker showdown, the Witch finds out his girlfriend told Dean, Sam and Bobby how to kill them. When he ask why, she says, "You know why. You know" and started playing with her necklace again. SHE NEVER ANSWERED THE DANG QUESTION. Why did she try to help them knowing she was risking her life and her boyfriend's?