I didn't see it that way. I interpreted it as her character making a point regarding something in her past. It didn't come off as funny, though, and it appears to be an outtake. Often time actors will find humor when they are unable to nail the lines and try to ad lib.
I didn't see it as belittling people who have tinnitus, either. She was not making fun of people who suffer or commenting on people whose lives have been severely impacted.
Comedy is rife in humor regarding physical afflictions. Remember the Seinfeld with Marlee Maitlan as the lip reader? Or Elain pretending to be deaf to avoid conversing with the cabby? Plenty of jokes regarding blind, deaf, etc. And it's not belittling.
Not trying to argue here. Just making a point that often we might see what we want to see, and feed our own negative emotions.