Brief Answer:
she may be having an allergy

Detailed Answer:
Hello

Since her adenoids and tonsils have already been removed , and she is still having a blocked nose, it is likely that she is having an allergy.

Allergy will give rise to constant nose block and sinusitis which will cause headache.

I would like you to meet an allergy specialist for confirming this .

He may ask you to get some blood tests , allergy tests and x ray of the nose done , please do them and follow his advice.

For the time being you can ask her to put saline nasal drops in the nose and take steam inhalation 2-3 times a day , it will reduce the block and she will feel better.

Take care

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Brief Answer:
It does not cause migraine

Detailed Answer:
Hello

Allergy is not likely to be the cause of migraine!

In fact , i personally think that she may not be having migraine and it may just be a sinus congestion because of the allergy.

Sprays are pretty much safe and i dont think you should avoid them,!

Please avoid self medication and meet an allergy specialist , he will find out what exactly she is allergic to and guide you better.

Thanks

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