Weiss tended to be on the shy side.
Even the simplest shows of affection would have her pale cheeks dusted a pleasant pink, which turned into a redder hue depending on the type of love you've shown her. She quite liked when you kissed each one of her knuckles, and a cheek kiss got her feeling a little flustered, but a direct kiss on the lips?
She would be a bit stiff at first, the feeling still new to her; sometimes she would still be in awe thinking about how you were all hers. She would try to relax as you teased her before about her tense, scrunched up face the first time you two had kissed. It still takes some effort not to be completely stiff-lipped, but once she leans into you, or grips your shirt/sleeve in her hand, you know she's gotten more comfortable.
You'll still tease her though.
She's too cute not to.