@TaxTim1 your answer might change if you reviewed the concept of equitable ownership and read reg 1.163-1(b).
Taxpayers who do not have legal title to a property may still claim a Schedule A deduction for real estate taxes and interest paid if they are the equitable owners of the property. An equitable owner is a person who has the economic benefits and burdens of ownership, based on the facts. Occupying and maintaining the home and paying the mortgage interest and taxes on it are factors that might indicate equitable ownership. Trans (TC Memo 1999-233), Uslu (TC Memo 1997551), Edosa (TC Summ. Op. 2012-17) Phan (TC Summ Op. 2015-1)
By the way while often cited IRS publications have no official standing. there was even a court case where taxpayers stated they relied on an IRS PUB. the PUB contained inaccurate info. Taxpayers lost.
https://www.accountingweb.com/tax/individuals/tax-court-grants-mortgage-interest-deduction-for-equit...
from the regs 1.163-1
(b) Interest paid by the taxpayer on a mortgage upon real estate of which he is the legal or equitable owner, even though the taxpayer is not directly liable upon the bond or note secured by such mortgage, may be deducted as interest on his indebtedness.
it is unclear if the daughter would face any tax issues if her mortgage debt exceeds the limits under IRC 163.
