With how perfect she was supposed to be, that "I forgot" scene doesn't fit.
IMHO she went back home to check on her son, knowing that she has work to do. After all she really did love him in her own, kinda autistic, way. Like, for all that acting she did, she forgot how to be herself. The closest scene to it was when she was already at the deaths doors in the hospital and trying to "play" a real family with Yuu.
Also goddamn Kazuki, you really can win at this point with first kiss and now this.