So my sister just found out that she was assigned a double room with washroom in McKay Hall, but she isn't sure if the washroom is private between her and her roommate or if it's shared with the floor like a common washroom.

Thank you

It's kinda both. The way rooms are laid out are if you stopped where each washroom was, there would be 3-4 rooms nearby. It's private in the sense that only one person can use that bathroom at a time but public in the sense you could technically use any washroom on the floor you wanted (heck building too =P). As a comparison, the washrooms in Whidden are like community centers. As for privacy, you can choose to leave stuff in there if you want such as your personal care products but that is up to you.

If its a "double with a washroom" wouldnt it just be for her and her roommate? if it was a communal washroom that anyone could use wouldnt they just be assigned to a "double room"?

Depends on the building you are in and also if apartment / traditional. Like I said above, the communal washroom is when 5 people can be in the washroom area at a time like a community center. For a washroom like Mckay, you can only have 1 person in there at a time. (single toilet+shower)

The bathrooms in Mckay are private, like the ones at home, but shared for everyone that has access to the building. It works great because if the 2 bathrooms near you are taken, you walk like 15 ft down the hall and there are 2 more.

if it specifically says 'double with washroom' then it is private. there are 2 double rooms per floor (one on each wing) with a private washroom - sink, toilet, shower, mirror - attached in the room. I'm a residence cleaner, and my team has been cleaning McKay for the past few weeks