Thank you for the info--TonyHi. Are you trying to prevent your cat from getting mosquito bites or trying to treat bites she already has on her nose? For a repellent, I have heard that Vet's Best Natural Mosquito Repellent is OK to use, but have never tried it. I have also heard that the oil made from catnip, called nepetalactone, is a natural mosquito repellent.
For treating a bite, you could "buy a box of plain, unblended chamomile tea [bags] from your grocery store. Brew a cup and chill it in the fridge...use it as a wash on the area, applying very gently with a soft cloth...chamomile is antibacterial and anti-fungal, as well as wonderfully soothing to pretty much ALL skin ouchies and surface wounds... buy the tea bags because ALL commercial chamomile tea is made from German chamomile, which is medicinally active and is safe for cats...ENGLISH chamomile is pretty useless medicinally, and is actually toxic to cats. Since the two look very much alike, buying the tea bags takes the guesswork out of it." (Courtesy of Mamanyt1953 ) You can apply the tea to her nose multiple times a day.
If you think that there is any possibility that your cat is allergic to flea bites, then I would recommend having your vet check it out. If her nose is raw or otherwise looks abnormal/irritated that can result in an infection that would need to be treated with antibiotics and possibly a steroid shot to offset the allergic reaction.
Done already--thanksIf your cat gets mosquito bites remember that this is how heartworm is transferred so please get her on some heartworm prevention asap!