She laughs delightedly as James chases Harry around on his miniature broomstick. She marvels at hoe similar her husband and her son look—except for the eyes, everyone tells her. He has your eyes.
She will never regret skinny-dipping in the lake with Alice, only to have Professor McGonogall catch them and give her her first detention in her life, and have to sit in a dusty classroom with the giggling Alice and, not surprisingly, all of the Marauders as McGonogall looks at them all as strictly as she can, but they know she's amused on the inside.
Because then, she wouldn't have felt so daring and carefree. And she wouldn't have ever said "Yes" when James Potter had asked her out for the very last time.
Her only regret (and it was very slight) was that she had not done so sooner.