Nishka Choudhury isn't on any rosters because her mom didn't make an account because she'd rather pay by check. is there a way she can make an account and enroll in the class and just not put her card information so she won't get charged?

-> no. You can have them sign up for a free trial, and we can treat that as their real account. We will need the payment method on file, as a backup to the check payment method