i don't know if you need to be worried per se but i would investigate this further. Why has she not been tested/diagnosed? People can shy away from labels but labels can help steer them to appropriate information and resources. Without knowing for sure what is going on, adequately addressing her needs is questionable.

i have a daughter with autism who is 20 years old. She has imaginary friends that do not interfere with her ability to function. i have viewed this issue as a benefit to her ability to work through her day as well as her ability to communicate. However, i've also consulted with her doctor to make sure there wasn't something further i should investigate.

What you're describing is a variation in skills that goes beyond what i've experienced. Regardless of cause or effect, the very fact you've questioned whether you should be worried is answer enough. You ARE worried and, therefore, you should seek additional professional assistance.

In light of the fact she has not been formally diagnosed, i would consider first discussing your concerns with your/her physician and then requesting a referral to a neurodevelopmental and/or neuropsych specialist. Hallucinations should be ruled out as well. They are not in and of themselves cause for alarm unless she experiences command hallucinations which could put her at risk.

Best wishes for you and yours.