If your mother has no intention to give a share to your sister, then she can execute the settlement deed in your favour as the land has been acquired on self acquiring basis even though you have financed it. In such case your sister can not make a claim on the land purchased by your mother.
Agreeing with what Mr. Krishnan stated your mother can certainly make a settlement deed in your name of the land purchased in her name as her self acquaired property though the same was financed by u. If a settlement deed is executed by your mother in your favour then your sister cannot make any claim over the property questioning the settlement deed. But if your mother does not make any kind of such settlement deed then later on your sister too will get a right to share in the property.