Will a Christian woman who has embraced Islam be held accountable if she delays or misses prayers for fear of her family finding out?

The original principle is to perform each prayer at its designated time, as Allah the Almighty says: "Indeed, prayer has been decreed upon the believers a book [i.e., obligation] of fixed times." It is not permissible to delay it except for a valid excuse. So, if she is able to pray at its designated time, she is obliged to do so. If it is not feasible, it is permissible for her to combine Dhuhr and Asr, and Maghrib and Isha. If she fears the expiration of the time for a prayer that cannot be combined with the one after it, such as Asr with Maghrib, she should pray Maghrib in whatever manner is feasible. It is not permissible for her to let the prayer go beyond its time. As for abandoning prayer altogether, it is not permissible and constitutes disbelief.