Old dogs, like people, have a harder time adjusting to change.
My 14 year(s) old got demented and followed me everywhere to the point of exhaustion. Some I have euthanized when their brains went haywire as no one had quality of life, whether us or the dogs themselves.
For now make her life as predictable as possible, maybe crate her more often if she is crate trained at all. She is not mad at you, but more likely keeping a close eye on you that you interpret as "being mad" because you feel guilty (?).