She's slightly allergic to herself (I suspected that.) My vet gave me some antihistamines to give to Mei twice a day (YEAH! Giving a cat a pill is my favorite thing to do!!!) and told me to come back next week for a progress report, just in case it's asthma. Apparently between the ages of three and five, cats can start showing signs of being asthmatic (Mei will be four in October.) Besides that, she's a healthy cat who just had big can of wet food and is back to being happy with me :)
P.S. Thank God for pet health insurance!