Why does Madam Morrible shake her head at Glinda in Emerald City?

While Elphaba is tearing the Wizard a new one, Glinda looks over at Madam Morrible. It’s one of those horrified “is that true??” looks. Morrible surreptitiously shakes her head no. What is her meaning here? Is she denying what Elphaba is accusing them of so she can keep Glinda on her side? Is she hinting that the Wizard is not responsible because she wants credit for the plan?