If you are Personal Rep. then you are in chnareg of when and what to liquidate -- within the ethical obligations of a Personal Rep . So long as you abide by the duties and responsibilities of your position (including but not limited to: doing what yu can to not let assets waste or depreciate; making yourself aware of all claims and judgments , tax liens etc. against the estate and/or your mother; paying all legitimate debts owed by the estate if the estate is solvent; filing an acurate Inventory Report and First and Final Account when each is due; waiting until the 6 montsh creditors and 6 month caveators deadlines have both passed and until the court approves your Final account before disbursing to the heirs the assets that are left. That said, there is a legitimate argument your sister might make if, for iinstance, you are living in mom's house rent free, for your own personal convenience, without haivng any personal ownership of that house, without paying any rent to the estate. If that is the case, you might end up owing the estate rent money if this sister objects to your not paying rent. Unfortuneately, the probate process is guided by legal principles and cannot be used by a Personal Representative to punish siblings who were not help at all to Mom, as she sees fit.
You may want to hire probate counsel to help you with this. Your half-sister can cause some problems and an attorney can assist you in making sure that you are taking the proper actions.