Unless a father's Will or original title deeds explicitly gave exclusive terrace rights to a specific floor (e.g., specifying that the second floor includes roof/terrace rights), the open terrace is legally treated as an undivided common area for all floor owners.
The law of equity states that if a person stands by and knowingly lets another person construct structures, spend money, and occupy space without protest for a long time, they cannot later demand demolition or partition.
Since you have openly, continuously, and exclusively built upon and possessed the roof space since 2008–2009 (exceeding 12 years) without permission or rent to the co-owners, your title over that specific built portion has matured through adverse possession. Her right to challenge your physical possession of those built-up areas is extinguished by law.
In many urban property arrangements, the owner who owns the topmost built-up floor implicitly holds the practical access and roof rights of that top ceiling, subject to providing utility access (water tanks) to lower floors.
If the first floor has not even been legally transferred/mutated into her name via a registered gift deed, probate of a Will, or relinquishment deed, she lacks full legal standing (locus standi) to institute a suit for property partition.
Ensure that the lower floor owners still have unhindered physical access to reach their respective water tanks on the roof. Fulfilling this basic easement obligation makes it nearly impossible for her to win a claim of hardship or denial of rights in court.
