Simplify the following text for a Grade 10 native English-speaking person.
Original: Her diary , published as the anonymous blog Belle de Jour : Diary of a London Call Girl became increasingly popular , as speculation surrounded the identity of Belle de Jour , and whether the diary was real .
Simplified: Belle de Jour is said to be the pen name of a former London call girl . Under this name she maintains a successful blog , Belle de Jour : diary of a London call girl which by 2003 had been selected by The Guardian as its blog of the year and has had two books published in both the UK and US