Can someone be too sweet and flawless or is it too good to be true?

Anonymous
My brother is currently dating his girlfriend for 7 months now. The girl seems well mannered and too sweet and flawless to the point I'm wondering if this is too good to be true or if someone can be naturally nice at all times.

To give you an idea of what she's like; she seems like a grown-up version of Lila from the Hey Arnold cartoon series. https://hero.fandom.com/wiki/Lila_Sawyer

She sounds like a real life Ms Perfect. Neither my brother nor anyone has ever seen her get upset ever. Is there such thing as a very sweet and flawless person or do they have a dark side too?
Updates
1 y
She fits too many categories; great cook (better than me), good at telling jokes, good at clothes, good at intellectual conversations, too kind, etc... good at everything and too sweet. Is this even real or do they have flaws too?
Can someone be too sweet and flawless or is it too good to be true?
1 Opinion