Since your sister’s name is on the car, thus she has insurable interest in it, she should be able to get insurance on it. However, most insurance carriers and state laws will require it to be registered and insured in the location the vehicle resides (typically 7 months out of the year).

To find out what an IL insurance provider will require of her, she can get a car insurance quote here.

If she does need to register the vehicle in Illinois, where she is residing, she can read information how to do so at the Service for Motorist section of the Illinois Secretary of State’s site. Here it does state that if you are new to IL you must change your vehicle registration and order new license plates within 30 days.

Illinois has a mandatory insurance law which requires you to have vehicle liability insurance in the following minimum amounts: $20,000 - injury or death of one person in an accident, $40,000 - injury or death of more than one person in an accident, and $15,000 - damage to property of another person.