Tamzin overdid it a bit
Sure it's a historic soap opera and Catherine Howard was a young, silly fool. But my goodness Tamzin was wayyyyy over the top silly, ditzy, giggly and DRAMATIC it made me squirm a bit. I actually cringed a few times watching her. There was just no subtlety in her performance and the laughing and giggling was just too much for me.
Anyhow, she is very beautiful and loved her clothing and she had good enough chemistry in the few quiet moments she had with Culpeper and Henry. Just couldn't take other parts of her performance.