Definitely something reading-light (unless she's pretty advanced) A lot of reading is boring for a 7 year old so I couldn't recommend a Zelda game just yet.
Your standard Marios and Kirbys are safe bets. Style Saavy and Cooking mama are also good series for young children and girls. If she isn't easily threatened, Metroid Samus returns has like, less than 500 words of text and it isn't *too* difficult to control.
There's also games like pokemon (if her parents are okay with that. I know some are kinda scared of it because of misunderstandings), smash, minecraft which are pretty easy to understand.
Obviously avoid any kind of RPG, including the Mario and Luigi series. Too much text and slow paces aren't great unless she's an incredibly adept reader.
Above all, I wouldn't put *too* many games on there. It's easy to get overwhelmed with the amount of games so I'd say gift her some as she beats the one's she has. She'll play the most out of what you give her.
Finally, make sure her parents are cool with this move. Obviously, you're being really genrous and that's great. Some parents are kind of strict about screen times and video games though and you don't want to accidentally upset the setup their family has going.