You cannot say ‘You should inform’ or ‘She informed’. You don’t merely ‘inform’, you ‘inform someone’ of something. You have to let the listener know who that someone is.
Examples: “I informed Bala that there would be a meeting tomorrow.* “The Principal informed some of the students that there would be no school tomorrow.” * ” The Manager informed Madhuri that he was taking the rest of the day off.” * “The teacher informed me that I had done fairly well in the test.”