Queshire
Istar
Aren't flaws just imperfection characteristics in the character? They don't necessarily negatively affect the character's lives.
If it's just flavoring then no they don't have to negatively affect the character, but if you're using her sex drive as an example of how she's not perfect then just that sort of flavoring flaw isn't enough.
Frankly any major aspect of a character ought to have some combination of the potential to complicate, simplfy, positively affect or negatively affect the character's life.