One day on the road from Winterfell to Kings Landing, you and Arya went through all the bogs and marshes to pick flowers. When you emerged you were both covered in muck but grinning and holding two large bouquets of wild flowers. Arya gave hers to Lord Eddard and you give yours to Jamie to see what his reaction was be since he kept giving you flowers. To your surprise he took them gratefully and kissed you softly. Your attempt to embarrass him backfired.

When one day you looked up from your readinv and smiled warmly at him, completely changing his mood from foul to happy. Even though for you it was a small thing to do it made him realise that he truly does love you

One day Sansa managed to get you to wear something fancy and 'civilized'. It was way too small and you could barely breathe but the look of disgruntlement on your face made him laugh.

You were eating and roaring with laughter at the same time. Kinda disgusting but your genuine joy without reservation made him realise that what he felt was a lot more than just a small crush.

When you were both young and you had to comfort him when he heard about his father and brother's deaths. You held him while he cried and comforted him and made him feel like the world wasn't entirely over.

On your wedding night you showed him that you are more than just an innocent little flower. This surprised him and made him feel something for you in his heart.

When you were walking down a stairs with several books in your arms and fell headfirst down them. You screamed out for someone to save the books, completely ignoring the hard stone steps grating your face to shreds.

She didn't love you and never would. Cersei only truly loved four people, Jamie, Joffrey, Myrcella, and Tommen. You are aware of this. But while she doesn't love you, you know that she definitely felt a small amount of affection for you. There never was a specific time when she realised that she felt something for you. It crept upon her slowly, growing everyday.