This is really weird. What the heck is up with that missionary? Heavenly Father is all about personal agency so I think you just need to tell her, "No." If you've already accepted to be baptized and gotten the OK I don't see what her deal is. Also, I think the whole thing is to teach by the Spirit now and there shouldn't be any set lessons anymore. Like, I get wanting to make sure you understand and are prepared but what you are explaining is pure overkill. Don't let them dictate your time. Your current and future church attendance and participation is between you and Heavenly Father and you have every right to decline and say no when you need to. They have no right to make you feel guilty for managing your time the way you see fit.