Emilia's parents had her very late in life after losing all hope to have an heir the normal biological way and not finding any child that met their demands in the adoption pool (that says something about those demands). Emilia was a wish granted by a Wishing Well to which Mr. and Mrs. Ernest gave an ungodly sum of money as offering hoping for a prodigy. Instead they got a cheerful clumsy blonde girl.
Emilia is a changeling, Fairy in a human body, like any other child acquired through magical source, though it's not common knowledge. The girl has always been unaware of her true nature same as her parents who couldn't however miss peculiarities in her behavior like sleepwalking, weird interest in nature and science that manifested in unsanctioned experiments on houseplants, little animals and kitchen appliances, as well as occasional telekinetic accidents. Instead if figuring out the cause Emilia's parents tried to make her as "normal" as possible by controlling every aspect of her life. Skills, hobbies, friends - everything had been handpicked to push the girl into becoming someone she wasn't and was hardly ever going to become.
As a result, she didn't quite become anything at all, lacking interest in what she was doing and lacking backbone to rebel and pursue her own aspirations. She did however develop perfectionism as response to her parent's hard standards and expectations. Emilia's parents passed away soon after she graduated from high school leaving her a decent inheritance that she never claimed for a number of personal (if not quite rational) reasons.
Emilia discovered the Magic Realm a couple of years later. As a Fairy she has natural magical abilities that are stronger than with most humans and she's making a rather fast progress in training, however her focus is mainly Practical, Alchemy and discovering uses of magic for medical purposes. She shies away from Mischief magic, while she could probably be good at it for Fairies are known as masters of illusions.
Soon after becoming a witch Emilia met an aspiring duelist coming from an old and powerful magic bloodline. Their romantic relationship somehow spiraled into engagement, but Emilia said yes for the fear of saying no, and luckily she realized it was a mistake soon enough. She had had similar problems before that, accepting what her heart didn't feel like and getting hurt and disappointed afterwards. It made her rather insecure about the whole relationships thing, however didn't stop her from believing in love.
Currently, Emilia is a student in UBrite Biology degree and is planning to become a Doctor. After a magical overload accident she was kicked out of university dorm and moved in with another young witch Rei Midoriyama.