She is going to get married, and her hymen was broken without her committing any immoral action
So long as you are chaste and have not committed any immoral action – praise be to Allaah – then you do not have to tell him, and you should not worry about that. The hymen may be broken due to jumping, insertion of fingers, heavy menses, lengthy spinsterhood and other reasons that the fuqaha’ have mentioned.
See: al-Mabsoot (5/8), Kashshaaf al-Qinaa’ (5/47) and al-Fataawa al-Kubra (3/88)
The husband should think well of his wife if he finds out that she is not a virgin. As we have mentioned, virginity may be lost due to causes other than immoral actions. If we assume that he asks you, you can answer him in a way that will ward off doubt from his mind. Rest assured that Allaah will support His believing slave and help him. See also question no. 40278.
The Standing Committee for Issuing Fatwas was asked: A Muslim woman had an accident when she was small in which her hymen was broken. She has got married but the marriage has not yet been consummated. In another case, a woman suffered the same accident, and now religiously-committed brothers are coming to propose marriage to her. They are both confused about their situation. Which is better – should the married woman tell her husband before consummation of the marriage or should she keep quiet? And should the one who is not married yet go ahead with it, lest it become known and people think badly of her? This happened when she was small and was not yet accountable. Or is this regarded as deceit and cheating? Should she tell those who come to propose or not, for the sake of getting married?
They replied: there is no shar’i reason why she should not conceal it, then if he asks her after consummation of the marriage, she can tell him the truth. End quote from Fataawa al-Lajnah al-Daa’imah (19/5)
We ask Allaah to help you and guide you.
And Allaah knows best.