First of all, thank you for your questions. This will help clear it up for others as well.

Calamity has Dissociative Identity Disorder, commonly known as Multiple Personality Disorder. The Dissociative part refers to when the frontal lobe of her brain shuts down (happens when under copious amounts of stress, such as trauma or fighting the switching between alters or personalities) effectively disabling any ability to remember the events that occurred between the switch and the switch back. I've written that she's already tried the medications, the cognitive therapy and the self-control exercises across the span of her life so far. Cal has little-to-no control over her switches as she has a rather severe form of the disorder as a result of her trying to create herself another life when she was young. That 'alter ego' became her reality in the fractured state of her mind, and lo behold, as she already had a chemical imbalance, she formed a disorder. This is a common way for people, especially those who have been under trauma or relentless stress to form such a disorder.

And I'd like to add that aside from her disorder and her past, she really is a fairly simple, lovable character. Her 'core alter', or main personality, is just a beautiful, well-educated make up artist/former nurse who knows she's beautiful and flaunts that in company. She chooses not to bring up her past; she's recovered from that. I don't know how deep your understanding of the disorder goes, but it's a consistent mental war between different versions of yourselves fighting for attention and dominion. It's sort of intense and very tiring. It's quite the something to see someone who has fought themselves their whole lives, and the Doctor appreciates her. The phrase 'complex beauty' was used to describe not her, but the storm beneath her skin, as a metaphor. I left it up to readers to decipher that however they wanted. And, as with most cases of MPD/DID in which the person self-harms, only one of her alters has the capacity to hurt themselves. It wasn't a common occurrence after she graduated Earth uni with the Ponds, but when you think about it - she would have been clean for that long, only to find out that she'd done it again. She would have been so proud of herself for staving it all off. And it wasn't even really her fault. Her temporary insanity is only the by-product of her disorder, and with such an extreme disorder, it defines everything she is. Just another girl with a hard life who didn't deserve it.

People have also drawn parallels between her and Clara; while I must say they are similar in their sass, Cal was created to be a foil to all Clara's future plans. That's why I had them share Clara's most loved aspect of character, to ruin any individuality she used to have and therefore confidence in that individuality.

I hope you understand my intentions for Cal a little better now :)