There's a couple of ways you could go with this. First, you could simply set one account to auto-forward to the other one, and then set up a filter in the first one to either just land in the Inbox or go to a folder just for that other account. OR------
You could add her account to the section in the left folder pane called "Add mail account", which is a very good mail-fetcher. Then her emails will show up there, and she can even see all the folders in her account. I'm assuming you are both going to use the same sign-in credentials for your account?