I am so sorry for your loss and for the problems that you are having.  You sister, as the executor of the estate, has the power and the duty to do what she believes is necessary in the probating of the Will and in carrying out the wishes of your Mother.  She can not, however, do anything that would create a breach of her fiduciary duty.  Now the way that you have phrased the question I think that you think that she is taking what she wants and leaving the rest to be sold, which is against the wishes of your Mother.  If you believe that she has not properly inventoried the assets of the estate and is in fact in breach of her duty you have the right to challenge her and to ask for an accounting of the estate assets.  As for the house, yes, she can change the locks.  Good luck.