Daughter seeing her father having relations

If a daughter looks at her parents having sex through a small hole. She was young and saw her dad's penis erected and looked for a little while and then felt discharge within her while looking. She can't remember exactly if there was lust with in her but she just looked at her mum and dad having relations and saw her dad's penis erected. But can't remember exactly if she had lust or she looked just so. But she said she don't think she would have lust for her dad. Is her parents nikaah valid?