I don't remember episode name but this is when Kevin dumps Robin. This is how i think her convo with Teddy Westside went

She stares at him for a moment before giving in. "No" she says honestly and Ted places his coat on her.

"If you don't want to tell me its fine…" Ted starts to babble and Robin puts a finger to his lips.

"No…you should finally know the truth Ted" she tells him. They sit and she puts out her cigarette.

"Remember that Christmas you made that light show for me because I was so upset?" she asked.

Ted nodded and the understanding showed in his eyes. "I knew you were lying" he murmured. Robin chuckled lightly.

"You know me too well Ted…" she agreed. "I was lying and I'm sorry…truth is I had found out that day I could never have children" she added.

"Wow…that sucks…I'm so sorry" Ted replied. He put his arm around her and she snuggled up to him.

"Yeah…I mean its not like I ever wanted kids but…its nice to have the option you know?" she replied.

"What happened tonight Robin? Are you and Kevin done?" Ted asked and she nodded.

"He had proposed to me then unproposed when I told him I don't even want a child ever…he does though so…he let me go" she told him.

"Really? Wow…never thought Kevin would be a jerk" Ted mused. Robin only shook her head.

"No…Kevin was fine with it and so caring but…I…I had to let him go…I told him I just don't ever want kids so…left me" she answered.

"Still sounds like a jerk to me" Ted replied.

"Ted…"

"I'm serious Robin" he protested. "I mean sure I'd love two kids in my future but for you…I'd be happy just having you for the rest of my life" he added.

"Thanks" she answers.

"I love you Robin" Ted replies and she gasps.