If I know AR-Kayn, both above are right. Mother asks the Daughter to use the elevator for her, but only the daughter ages up. It will also be a jump cut AP rather than shown (much as I'd love to see Kayn do a proper AP in this). They'll run into the other two ladies on the 32nd floor, and the APed daughter will pretend to be the mother much to the real mother's chagrin.
Then the two ladies will take the elevator back to the 2nd floor and the series will end with a quick AR of the two of them.