Some folks on the board are mixing up SSDI (disability insurance) with SSI (a form of welfare for low income folks). SSDI is NOT a "means tested" program. Means tested programs are those in which the payments are dependent on your lack of income and assets. DOCAR correctly mentioned, if it is SSDI then she could inherit a billion dollars and not lose the SSDI payments because it is not means tested. SSDI is not concerned so much with the amount of your assets or income but whether or not you can work.
Earned income is a problem for SSDI not so much because of the amount you get but because it indicates you are capable of doing work. So, earned income can cause you to lose the SSDI because that means you've been working. There is some amount of earned income a blind person can receive and still get SSDI under the special rules that apply for blind individuals.
SSI, which is not based on disability but is instead a form of welfare for low income folks, is means tested. Thus, if you get anything over a fairly small amount of assets or income, you lose the SSI. As DOCAR mentioned, there might be a trust arrangement that could help with that.