She is trying very hard to be like her brother, who is superior to her.
If you look very closely, her right eye is a shade of purple, instead of blue. This was a mutation in her DNA.
The reason why Invader LiAnn does not know her exact age is because during one of Invader Meen's time-traveling projects, she was chosen by him to test the prototype out. Something went wrong with the main motherboard while she was in it, thus sending her whirling into the past. Or was it the future? No one is sure, but thankfully Meen found her wherever and whenever she came out of the vortex. Mostly on accident. No one knows how much she aged during that time, whether it was five minutes or five years.
She used to know Twylyt under the genius name "That Dude". They were friends, if giving each other scars from shoving the others faces in air ducts counts as friends.