Other mistake: When Ana received her flowers the card facing her says Christian Grey Enterprises, when she reads the card to see who they are from it says Christian and she contemplated putting the flowers in the bin. Ana would have known they were from Christian when she answered the door because of the business card facing her.
Suggested correction: Who ever said she didn't know who they were from? When the delivery man gave her the flowers, she gave a look as if she knew they were from Christian and was probably thinking of him while looking at the card. Nobody said she didn't know who they were from, or that it was "revealed" to her, because who else would be sending her flowers, especially after a break-up?
Suggested correction: Just because it's right there in front of her, doesn't mean that she saw it, or registered it.