8938510
I assume you mean lines like:
"You look tastier than a blueberry muffin" Sunset Shimmer smiled.
From my experience in writing and reading, there is no periods/full stops at the end of dialogue. Of course exclaimation marks and question marks are there for shouting and questioning respectively.

8957505
When she’s performing an action, period.

"You look tastier than a blueberry muffin." Sunset Shimmer smiled.

When she’s voicing something, comma.

"You look tastier than a blueberry muffin,” Sunset Shimmer snarled.