The Brat is Reincarnated as a Princess

She's the only daughter and the only girl in their family, her name is Cwenne Thierry Veillet. A brat girl. It's her birthday and she was with her two cousin, they got into an accident.

She thought she's already dead, but God gave her a second life because she got reincarnated into someone else body, in a Princess of the other world's body! But what is really the truth? Did she really got reincarnated? How did she got into the Princess body if it is said that the Princess had just sleep?