How can a girl who has reached 15 years of age and begun her commitment overcome her feeling that the past years of non-commitment have been lost and cannot be compensated?

You must adhere to righteousness and commit to the obligatory duties and abandon the forbidden acts as soon as you reach the age of accountability, upon the appearance of any sign of puberty. This includes the matter of the hijab, for it is an obligation. We advise you to make abundant supplications and to hasten towards righteousness, for life is limited and one's appointed time is numbered. Do not pay attention to the whispers of Satan that discourage you from pursuing the path of good.