Your friend will be fine. I don't know what kind of ostomy your friend has but TN to NC is an up and down flight, that maybe will be an hour and a half flight tops. Just tell her to use the bathroom before she gets on the plane. I've never heard of the cards before.
It's not a bad idea to have a change of clothes and 1 or 2 precut pouches or 2 piece or what ever she uses, as well as some wet wipes in her carry on.
I have an ileostomy and I travel all of the time. Here is what your friend can expect and her options.
You can opt to have a private screening first and foremost. You just tell the TSA agent that looks at your ID/passport and boarding pass that you prefer a private screening. I personally don't think that's neccessary. But for peace of mind and if your more comfortable with that, they will oblige.
The new scanners will pick up the ostomy and what usually happens is a TSA agent will take you aside, you tell them you have an ostomy. They will then take you aside, ask you to rub both palms on the ostomy over your shirt or blouse. They will then take a flat sample swab, rub it on both palms and then they put the sample in their analyzer. The analyzer will not detect a threat and you will be on your way.
Smaller airports still only have metal detectors and you won't even have to worry. I myself signed up for TSA Precheck. It only costs about $140, but I do that because I travel frequently and most of the time, you go through the metal detector instead of a scanner. And depending how long the flight is, I don't eat anything until about an hour before I get on a plane, if at all. This way I know my ostomy won't have output for about 4 hours or so. I've had some gas expand the bag a tiny bit but it's nothing.
I hope this helps your friend in some way. Please let me know if you have any other questions.