I looked on turbo tax and found this about claiming an adult child:

"The Irs changed the definition of a qualifying child to these five steps a. the child must be a son, daughter, sibling, eligible foster child, stepbrother, stepsister or a descendant of any of them. The child must be under 19 or a full-time student under 24 or someone disabled of any age. The child must have lived with you for at least seven months or more. The child must not provide more than half of their support for the year. If the child can be claimed by more than one person, you must be the entitled person.
The qualifying relative has four steps that define this term. The person cannot be your or anyone else's qualifying child. The person must be a member of the household all year or a relative. You must provide more than half of the person's support for the year and the dependent must have earned less than $3200 for the year."

You might be eligible as a dependent IF you have been determined to be disabled but I don't know who or what agency would have had to make that determination. I looked into this out of curiosity, not b/c I am going to turn her in. LOL