Please be aware that the housing loan shall be granted only if you are the absolute owner or the same will be granted jointly to the owners if there are two owners by making the other owner s co-applicant.
If your sister is not willing to cooperate you may have to file a partition suit and seek separate possession of your share and that of your mother's share if she has relinquished her rights in your favor.
The bank will not grant loan for undivided share in the property for constructing a house.