Nope, she should be able to get a new TN that way without a problem. I never did it before, but tried to once when I was over working in India for a short time for the company I worked for. When I came back I was about a month away from my TN expiring and I enquired when I got back to the airport from the US. They said they were able to issue me a new TN, however being I still had a month left, they said I needed to wait till closer to the date. So if hers is expiring within a couple of weeks they should be able to still do that. Maybe they will still give her a new TN if it's a month away? Not sure what it's like now, but years ago, it was very possible and just the same as getting a new TN from driving to the border...