This could be a sensory issue. Some kids have a lot of sensory integration problems some have single sensory issues. My son has auditory sensitivity and can't be around microphones because of the amplification.
You need to talk to your doctor immediately because it could be a sign that there's more going on. She should be screened for a number of things. I don't want to alarm you, but you should ask for a screening for sensory integration disorder/sensory processing disorder and autism. The screening is a tool to decide whether to move on to the next step and go through the diagnostic process. Just because the screening indicates that you should move to the next step does NOT mean she has either sensory integration disorder or autism. It just means she needs further observation by your pediatrician. Ideally, in the diagnostic process, you should have a team of doctors who look at whether she has either diagnosis or not.
Please at least go through the screening to eliminate either of these possibilities. She obviously has a need to chew like this. You can't punish it out of her if there's something driving her to do it. Continued punishment or withholding of things she loves for something she may have no control over will only damage her self-esteem later on.
And, if it turns out that she has either of these diagnoses or something else is causing it outside her control, I know you will want to get her all the help she needs.
Note about Autism... many people think that you don't talk and don't make eye contact if you have Autism. Autism Spectrum Disorder has a range of behaviors. Some people with Autism don't have the "typical" or stereotypical characteristics, but have other milder characteristics of Autism Spectrum Disorder. The American Academy of Pediatrics now recommends that all pediatricians do a screening for autism several times before age 2, starting at 18 months. Your doctor probably has all the information at hand and can help you with this. Please don't hesitate to call him/her.
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