"That's great, Molly." Thomas nodded. He cared for Molly and her well being because she was important to Harry. And because while she had seen his entire life's tragedy story in that soul gaze, he'd seen hers. He knew who she was deep down, and possibly knew things about her she had never admitted out loud. It was an awkward thing, to share that kind of intimate knowledge with someone with a relationship like what he and Molly had.
"I'm happy for you." The sentiment was genuine. he was happy for her. He wished her the best, in everything. He knew she hadn't always had it, had often gotten the raw end of the deal in life.