Signs of Anakin’s pending dark side fall
Despite not seeing Anakin a lot during the war, Padmé would’ve noticed signs that could’ve lead him down the dark path. His constant butting of heads with Rush Clovis was one example. When the senator went to kiss his colleague Skywalker flew into a blinding rage but did not use the Force in his attack.
Padmé was forced to break the pair up and confessed she had grown frightened of her husband’s dark behavior. This lead to her temporarily calling time on their relationship until Anakin got a handle on his temper. She forgave him after Clovis sacrificed himself to save her from a collapsing balcony.
Towards the end of the war, Anakin’s demeanor changed to the point it was hard to determine what might happen next. However, when he started to experience visions of his wife’s demise in childbirth, this is where things began to take a turn for the worst.
Determined not to allow his wife and unborn child to fall prey to the same forces that took his mother from him, Anakin frantically searched for a way to save her. However, it came at the price of his soul when he pledged his alliance to Palpatine who issued him an empty promise.
When Obi-Wan arrives and tells Padmé that Anakin was behind the killing of the Younglings in the temple, she refuses to believe he would do such a thing. However, she knows Kenobi too well and has no reason to doubt his message to her. He loved his former student like only a big brother could and was willing to accept his flaws for what they were. But killing innocent people was not on and he had to tell someone who would believe him.