I really shouldn't be surprised. Mom is a very... energetic lady as we've seen.
Zekana said: well Yuu was dealing lots of psychological damage to takashi, even if unintentionally.
Well, I guess showing off multiple swimsuits, nearly stripping down completely and refusing to let him leave COULD be considered "going berserk" in a way.
Updated
...Yuu-chan, our little girl...Huh?May...Maybe...?Yuu-chan...went berserk on him...!You were just like that too...!Something definitely happened with her, right?You... you think?going on, right...?I was prepared for that much, but...There must have been some ki... kissing...But since there's no way that Takahashi-kun would do anything like that... that... means...