It is not normal for cats to develope laryngitis. When this occurs, it is normally caused by a foreign object lodged in the esophagus or other area of the throat, or your cat could be developing a respiratory infection or bronchitis. She definitely needs to be looked at. Occasionally loss of voice can be attributed to oral cancers. Additionally, viral illnesses such as calicivirus and rhinotracheitis are probably the most common causes of upper respiratory diseases in cats and laryngitis. Hopefully if this is the case, your cat will regain her voice, too as these types of laryngitis usually resolve once the virus has cleared up. I read of a case report of a cat with feline immunodeficiency virus (FIV) losing its voice. If the signs persist, it probably wouldn't hurt to test for that (although it is probably an unlikely cause). I suspect that some cats just aren't speaking for willful reasons. They can be pretty stubborn at times. Since we can't ask, it is hard to be sure of this. Good luck and let me know what you find!