Hi Kaza,
Are you and your sister joint executors as well as beneficiaries under the will? And what sort of property is involved? Is it cash or real estate?
Once the distribution has been made, in equal shares to you and your sister she is free to do whatever she wishes with her half. So there is nothing stopping her ongifting to you. However in the case of real estate etc, if you do not wish to make 2 transfers (for example where there may be fees involved) your sister is able to formally disclaim her entitlement in which case I assume her gift would go into the residuary and if you are the sole remaining beneficiary would become your inheritance.