Speaking to Us Magazine, Preston explained that Paquin and Moyer have a wonderful relationship based on mutual understanding.
"They're really sweet with each other," she noted. "They just really get each other. Anna will say she's never been happier."
The actress, who plays Arlene on the hit HBO vampire drama, attended the couple's wedding at a Los Angeles beach house earlier this month.
"It was so beautiful. They seemed to really honour the show [True Blood] that day. [Co-star] Todd Lowe's band played and the script supervisor married them!"
The star added that she wished nothing but the best for the newlyweds.
"I wish them all the best for a long, loving and respectful relationship."