Yes, changing it to ten pm would be fine.
She can vary the time she takes it by a
few hours a day and that's okay, too. She
can take it at 10pm one day and 8pm the
next and 9pm the next; that little
variation isn't harmful.
Also, bc is completely effective no matter
what time of day she takes it. What, did
that person think that bc stops working at
midnight like Cinderella's carriage or
something?

She could take it at midnight for all she
wanted; if that time worked it would be
fine. Any time of day is fine as long as
you are consistent.