And probably she will separate the two in the future. Fearing the nightmares caused by her stupid son.
Wait which chapter did it show the twin getting bullied?
I'm sorry but I forgotten the specific chapter but Yeongwoon is the uke and the twin's mom thought maybe Seo-in (Seme) bullying him too cuz they where together when she saw them in the hospital (last chap). Additionally, they didn't show the whole chap or scene how our baby uke bullied by the deceased twin or Seo-in's brother (he is the bully in his high school years) that also showed in one chapter or last chap of S1 that the mother of twin's covered up her son's doing to Yeongwoon using money so Yeongwoon's dad won't say any single word about the bullying incident. Which there'll be a possibility that the past haunts the mother of twin's (conscience probably). That is why she Tried to approach Yeongwoon in the hospital because she want to say something to him. Season 2 for sure will be beefy and full of drama flashbacks.
Maybe Seo-In's mom also thinks that Yeongwoon is receiving the same treatment (bullying) as what his twin did before.