Clearly with Katie's history this has to be a real concern. I just wonder if it might be related to the Darwin heat and humidity. Things will no doubt become clearer in the coming days.
I wonder/hope the rule of thumb policy is low risk approach .. if there's any sign of a niggle, withdraw .. not much value in continuing for a W35 .. and consult her medical/therapy people in US .. and that she'll be back soon if she can be