They'll probably just think she's from MN or ND. ..eh?
In that case she'll either be from the MidWest (MN) or from the West (ND) -- both are better than being a Yankee. (Although, I do regret to say that many Southerners fail to recognize the distinction.)
OP...Tell your friend that she needs to understand the sacred drink, tea. If she orders tea in a restaurant, she will get a tall glass of sweetened ice tea. If she wants a cup of hot tea, she needs to ask for hot tea. (It will probably be hot water with a Lipton Teabag. A true friend would give her a case of RedRose or Earl Grey tea as a wedding gift.) Many times the sweet tea will taste very similar to simple syrup. In which case she can ask for unsweet tea. But beware: to ask for unsweet tea could very well raise questions about her origins.
Also: Curious mannerisms.
Southerners are family-proud and she will inevitably get questions about her name? For instance: Who are your people? If her last name is Fuddy...."Are you one of the Memphis Fuddy's or are you a Nashville Fuddy?" And then the search for relatives in common will commence.
The South fits squarely in the Bible Belt. She should be prepared with an answer for the inevitable question: Where do you go to Church? or Where is your Church home? It can pop up in the most interesting places...like when she's getting her driver's license! Religion is considered a proper topic of conversation in the South. Most of the time (but not always) it is the equivalent of asking which country club you belong to.
People just want to know which sandbox she plays in. Also, she should decide right now if she is already saved, wants to be saved or intends to be rude!
She will be addressed as Ma'am, or sweetie, or honey. Ma'am is also a question indicating the person did not understand her. Any social contact must go through multiple layers of polite gobbleygook before you get to the point of the meeting. Forget about getting a direct answer to any question. She will get the polite answer. The glass ceiling is firmly in place. Depending upon how "modern" the city is, living in the South as a woman, is much like living in Japan as a woman. Women have a great deal of power and control, but any woman who shows this is scorned. She should watch the movies Terms of Endearment, Fried Green Tomatoes and Steel Magnolias. Driving Miss Daisy would be another good one.
She should be prepared to be shocked at local pronunciation and grammar. There are a multitude of Southern accents and not all of them are charming. Also, she should brace herself for the everyday display of patriotism on a scale unknown in Canada. Americans are the ONLY americans living in this hemisphere.