She will either block her (as she is American and a smaller account so won't see her as competition) or will PM her with a "hey lovely I love your work I'm so sorry it just slipped my mind see I'm new to all this fame I'm just little old Sophie. I'm so busy with my two children full time job and house move" blah blah.Oh she fuming fuming, understandably.
Sophie will crack on with her night laughing away, pretending she's not seen it, she won't own up and she won't apologise. I can't stand her, I hope this blows up.