If you create a new (temporary) admin login for her in Tableau Server, does she see the same behavior using it? If yes, then I bet it is something associated with her environment - as you suspect. If no, then it could be the login / Tableau.
After more troubleshooting, some other users are reporting this issue as well. We have a QA environment that has a lot less activity than our test environment. I deleted the original reporter of the issue from QA, re-added her, and now she no longer is prompted with that login expired message.
However in test, she's the owner of many data connections and projects, so I can't delete her until she removes them...obviously this isn't an efficient solution. I tried to take away her site admin status and then re-apply it but that didn't do anything. Deleting her from Tableau Server and re-adding her corrected the problem, but we're hoping something else can be done so she doesn't need to remove everything she owns, just to be recreated and then add them all back again.
Interesting. You see this across all your environments (Dev, QA, Prod), or just QA?
At this point I think I'd open a case with support - there's something strange going on here and you'll probably need support to dive into your logs to figure out what that something is.
Good luck! Would love to know what the problem turned out to be if you feel like posting same when all is resolved.
The login prompt was occuring in the same fashion across Test and QA for her (Prod isn't up yet). I opened a support case and am waiting to hear back, so figured I'd try the forums in the meantime. Once it's resolved I'll post the details.