Sorry you are going through all this.

She may very well have some type of MI that could be her problem or she just likes how her life is. If she is able to qualify for disability then there would be medical records coming from some where to support her need for it. Does she see a Doctor often? Do you know of any medical problems she is dealing with? Being obese isn't going to get her disability. Due to all the Hippa laws it will be hard to find out if there is anything going on , besides what she may or may not tell you.

Good luck I hope you can find a solution.