And replaced by a doppelganger I think. She/it has started drinking fruit tea (formerly appalled by the idea), dyeing her hair (only a shade but always said she never would) and feeling like sex in the afternoon (previously only at night, in bed after a cup of proper tea and 20 pages of crime fiction). Small things I grant you but very out of character and they're starting to add up, she'll be liking romcoms next.
But it's possible that an extraterrestrial explanation is over-dramatic - anyone else experience this sort of thing on hitting their 40s..?