Why and how did Cooper suspect that Amelia Brand had intimate feelings for Wolf Edmunds in Interstellar?

Question

Cooper's first suspicion that Amelia has intimate feelings for Wolf Edmunds in Interstellar comes when they are on Endurance and Amelia is introducing him to the 3 planets that could sustain life. The conversation goes

Amelia: Laura Miller's planet is first. Laura started our Biology program.
Cooper: Hmm
Amelia: Ah... Wolf Edmunds is here.
Cooper: Tell me about Edmunds.

It seems this is the point of first suspicion. Why did he interject when Amelia would have given a brief background of Edmunds as is.

Amelia: Oh... Wolf's a Particle Physicist
Cooper: (judges Amelia's body language) None of them had families?
Amelia: No, no attachments. My father insisted. They all knew the odds of seeing another human being again. I am hoping we can surprise at least 3 of them.
Cooper: How about Mann?
Amelia: Dr Mann? He's remarkable. He's the best of us. He inspired 11 people to follow him on the loneliest journey in human history. Scientist, explorers. (getting emotional) That's what I love. You know, out there we face great odds. Death, but... not evil

By the way she describes Mann, I would think, that too as a wildest imagination, that Amelia had feelings for Mann.

Cooper than goes on to ask TARS, privately about them two.

Why did Cooper suspect Amelia had intimate feelings for Wolf Edmunds from this little conversation. How the hell did he suspect would be a followup question.

Answer 1

This is dealt with in the film's official novelisation. Coop notices that when she talks about Wolf Edmunds, it's with a slight inflection that suggests a deeper relationship:

“And Wolf Edmunds is here,” she said. And the way she said it, the way his name came off her tongue—Cooper had never heard anything like that in her voice before. As if that red dot was the center of the universe. Suddenly he was curious.
“Who’s Edmunds?” he asked.
“Wolf’s a particle physicist,” she said, and this time he knew he heard it. And the way she smiled…
Interesting…
“None of them had family?” he asked, pressing from the side rather than the back. He didn’t have Brand entirely figured yet, but he’d seen enough to guess that head-on wasn’t the right way to come at her.

TARS pretty much confirms this in a later scene:

“Were Dr. Brand and Edmunds… close?” he asked carefully.
“I wouldn’t know,” Tars replied.
“Is that ninety percent, or ten percent ‘wouldn’t know?’” Cooper pursued.
“I also have a discretion setting,” the robot informed him.
“So I gather,” Cooper replied. He stood up. “But not a poker face.”

---

You can also find a similar description of the scene in the film's official screenplay

She shows him a red world, just a tiny dot.

Brand: And Wolf Edmunds is here.

Cooper hears something in her voice.

COOPER: Who’s Edmunds?

BRAND: (fondly) Wolf’s a particle physicist.