I might ask her this - and I might not take the job if you feel that she really isn't open to listening to you, who has experience with newborn infants. Because if she's adamant that the baby can't be fed more than once a night, that the baby will be sleeping from 7pm to 7am, well - we all know that's not going to happen, and you'll be left holding a hysterial, hungry infant with nothing to do but try to soothe the baby, which won't work because he/she is hungry. And YOU will be stressed out not able to solve baby's problem and mother will accuse you of not doing your job.
Lose - Lose.
So if she remains this way, I would decline the position. Anyone who has done any reading on newborn infants (or who has talked to any of their friends who have babies) they KNOW that babies don't sleep through the night and need to be fed every 2 or 3 hours. Heck, my sister's husband even knows this and he doesn't know anything about babies (they haven't had any yet).