Cedric was initially upset because she was taking long to arrive, he was always a strict person when it came to training.
If she was determined to get stronger he was going to make sure she achieves it, no excuses whatsoever.
When she arrived at first he clearly sensed her presence but wanted to ignore her at first until he heard the knights silent whispers they had no idea he could hear.
How they fought against stealing glances of the princess knowing he would be against it. Clearly they were stunned at her appearance in the training grounds, Cedric thoughts maybe it was just because they never imagined the princess trying to train.
He didn't expect it to be something even he was uncomfortable with a subtle jealousy filling his heart.