The National Hurricane Center (NHC) website has all sorts of maps available when storms crop up.
https://www.nhc.noaa.gov/
Clicking on a storm will bring you to a page that looks like this. (Resized to fit better.)
In your case, you'll probably be most interested in the "Arrival Time of Winds" map. I say that because wind is going to be the chief determination of when an airport will close.
The NHC publishes two versions of the map. What you want is the "Earliest Reasonable Arrival Time of Tropical-Storm-Force Winds" map. (When a storm becomes a hurricane, you may see additional maps showing when Hurricane-Force Winds will arrive. Ignore those and stick with Tropical-Storm-Force Winds because that's usually the threshold airports/airlines use to determine when airports/flights are canceled.)
Current map as of 7:51pm on 9/8/18 (resized to fit better):
There is slightly different map that can be found by clicking options in the box that appears above the map. That changes the graphic from "Earliest Reasonable Arrival Time" to "Most Likely Arrival Time" of the wind.
Current map as of 7:53pm on 9/8/18 (resized to fit better):
What these two maps tell you is that airports and airlines will need to figure out what they are doing prior to your niece's flight on Thursday. That's because the arrival of winds strong enough to close down airport will be some point on Wednesday night.
As such, I would expect airlines to start offering weather waivers at some point in the next day or two. I would recommend watching the airline website for that waiver. I would also recommend that your niece plan on the fact that she will need to leave on Tuesday or Wednesday. Given the fact that both Charlotte and Chicago are major airline hubs, she shouldn't have too much problem finding a flight.
IMPORTANT: Forecasts are just forecast. They change. Many people in South Florida evacuated to the west coast of Florida due to the projected path of Hurricane Irma. But, Irma didn't follow that path and ended up hitting the west coast of the state.
