Initially i wasn't aware of Ms. Walker and her overall body of work, however after flipping though some of her photos, i was immediately drawn to her nose as the possible culprit in this plastic surgery mystery.
Ashley Greene before and after nose job
Before and after comparisons show Ms. Walker with two differently shaped noses, mainly focusing on the tip, which appears to be a bit curved in the after snapshot.
Sandra Bullock before and after plastic surgery
Other speculators have suggested the possibility of a minor facelift and facial fillers, however i strongly believe age and makeup are playing a key role in Ally Walker's current appearance. But i could be wrong, considering my familiarity is quite low with this particular celebrity.