Nala isn't too awfully big (almost 30 pounds last time we weighed her), but she is rough when she plays. It's difficult to teach her to play easy because I have a 6 year old brother that loves to play rough with her (despite my begging him to leave her alone, or at least not encourage rough play). She generally is only rough with him though (assuming she sees him more as a litter mate as compared to myself and the rest of my family).

But my concern is with my grandmother's new puppy. She hasn't gotten it yet, but she is getting a yorkie puppy. I haven't really socialized Nala with dogs much smaller than her, but I'm afraid she might hurt my Nanna's new puppy if we try to get them to befriend each other. Any tips or advice?

Soime dogs are good at knowing things are babies and go a little easier on them then if they were playing with a fully grown/adult puppy.

Having said that, I wouldnt leave the two of them alone in a room together until you are 100% confident that she is going to play nice.
I think introducing slowly may help, maybe through a wire door, so they can smell each other but not get at each other on neutral territory.

Freya is 9 weeks old and plays rough too. She does it with almost everyone as we are still learning not to with people.

I am dog sitting my mum's 11 year old maltese terrior for a whole week. I'm cautiously confident as my mum's dog is the older of the two and knows she is dominant over most other dogs, even with her small stature.