My eleven year old daughter is pretending to be sick and making her speech sound very strange. She has been doing this for 3 days and my spouse and I can't seem to get her to quit. She has "mistakenly" talked normal a few times but quickly faked ag

This is definately being faked yet it is causing my spouse and I to worry about mental illness. We have no family history on either side. She is a first child, she is eleven with a 5 yr old sister. We are very adiment about giving "equal" attention to both and we are very involved and loving parents. Please Help.