Hi,
What symptoms does she have? Is she on any medications currently? Has a CT scan of her sinuses been done? Is she allergic to any other specific substances? Has she had allergic reactions in the past?
The hat could definitely aggravate her symptoms.
She could take oral antihistamine medications like cetrizine or loratadine and see if it helps with her symptoms. She should also take steam inhalation and saline nasal drops several times a day.
If his symptoms still persist, consult a doctor because then she would need to get certain investigations done and would probably need steroid nasal sprays and a course of antibiotics.
Let us know about any other doubts that you have and post us on how she is doing.
Regards.
I have horrible ragweed allergies and wouldn't be able to spend much time next to someone with a ragweed hat. Depending on how bad her allergy is she may or may not be okay.