I know your original post is over a month old...but thought I'd answer anyway.
You can have two users on the pc version. Just go to file in the upper left corner and select "new account." It will have you backup your current account.
Then you can start a new account with or without having her set up an account online, and it will walk you through the steps.
After you have a second user account set up, you can easily switch accounts by going to file and selecting the appropriate name.
I do think that she will have to enter the custom foods herself, though. I don't believe they will be carried over.
I don't think you can track two people on the same account online, but I don't know for certain.