Can Survivor change the Living Trust?

In CA, father died, estate worth 8 million, Living Trust stipulates that 50% of the undivided village genuine estate is to be placed in to an Exemption Trust (for max fed 3.5 million exemption) as well as a additional in to a Marital Trust. The alternative 50% of a village skill goes in to mom's Survivors Trust which is revocable by a Survivor.  Living Trust indicates sister becomes Trustee on a death of a Survivior, however, sister not prolonged ago obtained POA, mayble durable POA (don't know).  Each of a children are to inherit dual or more specific genuine properties, thus, each kid receives appromiately a same worth in genuine property.  

Question:  If Survivor wants to revoke her Suvivor's Trust (and sell some of the genuine properties) who decides which genuine properties property stays in a grant trust, which, I pretence cannot be sole as prolonged as there is enough let income / money to compensate bills, etc.?

Question:  If usually a single or dual specific properties have been sold, how is a beneficiary who was to inherit those specfic properties compensated if there is no or little money accessible down a road, yet, the alternative genuine properties have been not sole as well as alternative chldren inherit them at full value.  Is there a requirement which a beneficiary receives as 50% of a worth of a sole property, given 50% of a estate was to be placed in non-revocable trusts? 

Question:  If Survivior wants to give a specific expensive very old to a single child, can the Living Trust be admended by a Survivor, and/or can she only give it to a kid prior to her death.   

In alternative words, what are the Survivor's limits given 50% of a village is suspect to be hold in a non-revokable grant as well as marital trusts.