What kind of breed is she? When she was confined post-op, how much time did you spend with her (e.g. was she alone in a room more often than she was before)? Does she have a history of being timid or unsure?
My initial reaction, without knowing details, is that maybe she was kept in a room that didn't get as much traffic so she may be a little un-socialized or may be have some separation anxiety. I can see how it may be hard to confine your animal appropriately in a room everyone frequents often.