Fridge Horror: At first glance Lalah's cheerful appearance seems out of place, considering her past is similar to that of another young lady. But then it's revealed that the Flanagan Institute considered her their star student and she was subjected to testing out Newtype weaponry, and later in Char's Counterattack Char reveals he regrets using Lalah like a machine. Adding this together, it begins to sound very similar to a certain girl in Zeta Gundam who was a Newtype guinea pig for weapons and subjected to massive amounts of torture and Mind Rape, while displaying an identical cheerful disposition that seemed off. No wonder Lalah seemed happy after she died.
Let's not forget that, before being taken in by the Flanagan institute, Char found Lalah in the streets. Who knows what kind of life she left back then.
