Peace be upon you. It is permissible, but it is strongly recommended to wait until after washing the area. According to Ayatollah al-Uzma Sayyid Sistani (may Allah protect him), it is allowed, but it is obligatory to wash the area first. According to Ayatollah al-Uzma Sayyid Khamenei (may Allah protect him), once she is pure, her husband may have intercourse with her before she performs ghusl, although it is disliked, and it is preferable to avoid it before washing. May you be successful in all good.