Is the validity of nikaah subject to repentance of past sins?

During childhood a woman committed sins. The sin was that the woman, who, in her childhood was a girl, rubbed her private parts on another girls private parts. The woman doesnt think she had underwear on when this happened but the other girl had underwear on. This sin happened either when she was 12 or under the age of 12. It happened before the age of puberty as she got her periods when she was 14. As she matured she realised that was a homosexual act and it was wrong.

The woman is married to a a good man, who has never done such sins in his past. and the woman has recently been getting doubts upon repentence. She read somewhere that if one doesn't repent for such sins or sexual sins before marriage then marriage to a person who has not done such sins in the past or marriage to a chaste person is haraam and not valid.

Was the marriage valid from the start? Was it haram to marry such a person who has committed such sins in the past when the other hasn't?