You can deduct medical expenses on your tax return that you pay for yourself, your spouse, your dependent, and any person who could be a dependent and is only disqualified by their income. (People who are disqualified from being your dependent for reasons other than income are not eligible for the medical expense deduction.)
The conditions for claiming your own child over the age of 23 as a dependent are (a) they earned less than $4400, and (b) you provided more than half their total financial support for the year. (If it is your own child, it doesn’t matter where they lived. It doesn’t help if they lived with you and it doesn’t hurt if they didn’t.)
Since the income limit does not factor into the medical expense deduction, the only relevant question is, did you pay more than half her overall living expenses for the year?
Her living expenses for the year include food, housing, tuition, medical expenses, travel and entertainment, and so on. If you supported her to the extent that you paid half her living expenses for the year, you can deduct medical expenses that you paid for her.
