I would image it still has to be a certain way - she would have to use the box it was purchased on, while you had to use the other one because then she's on the home console and you are "signed in away"
That's how it was on 360. On Xbone it's slightly different: The home console is tied to the account, not the purchase, no matter where the purchase was made.
That means it doesn't matter if the other account purchased the game/content trough the web site, the account's owner console, or the other console, the home console will receive the license right away.
English is not my first language, so I fell like I haven't been able to explain properly, so here's an attempt to make it more clear on how sharing works on Xbone:
Let it be:
Gamertag A, whose owner has console A.
Gamertag B, whose owner has console B.
During setup gamertag A has to chose console B as the home console. And gamertag B has to chose console A. And that's pretty much it for setting up. The content is now shared!
That setting now does not have a cooldown (of 2-3 months) like it used on 360, but unlike on 360 if you change your home console the licenses tied to it are revoked as soon as the console is online (or in stand by).
The owner of gamertag A while playing on console A never needs to log with gamertag B, all the purchases gamertag B have are instantly accessible for every account on console A. No matter what game or dlc you try to download, it will say as it was already purchased and ask you to install. The same is valid to gamertag B playing on console B. That might be useful if you don't trust the other person enough. You can go to the person console, setup up your gamertag, and ask for a password during login.
The drawback:
If gamertag C wants to play on console A, a content that is tied to gamertag A, you'll have to log with the account A (thankfully now there's no need to have a controller for each account signed in) so the console knows it can access the content. That has a further drawback: I've only seen in BF4, but the game, on console A wouldn't recognize that gamertag C has access to the season pass bought by gamertag A, even when the content is already installed and gamertag A is logged. Gamertag C would need to log in console B to be able to use the season pass.