That's it. That's Sam's one "not a flashback" appearance in this storyline.
(Sound of torches being lit)
I AM OBVIOUSLY JOKING PUT THOSE AWAY, YOU
When I originally imagined this scene, Ellen had actually chosen the right pep talk, and Grace had been wondering about what sort of difference she might have made had she been there at the mall.
Thing was, it didn't really make sense. Grace was exactly where she was supposed to be on Friday. She wasn't being irresponsible, the mall had nothing directly to do with her, she helped search for Elliot, Ellen, and Ashley, etc.
She might wish she could've done more to help, but she wouldn't feel personal guilt over it.
Thing was, I really wanted Ellen to say what she said to Grace, and I needed this moment of Sam fleeing, too.
Fortunately (or unfortunately, depending on how you look at it), Ellen has her own reasons to feel irrational guilt, and it would be natural for her to misinterpret what was bothering Grace.