My mother in assisted living receives social security, VA aid and attendance. How do we file a caregiver agreement with the VA?

My mother is 92, in assisted living and receives her social security and VA aid and attendance. We are now out of money for her to continue to stay at the Assisted Living. My sister and I are willing to provide in home care for her at my sisters home. I know that we need to file a caregiver agreement with the VA. But my concern is that we are doing everything we can correctly in order not to loose her VA benefit that we so need to continue to care for her at home. Need to know who we can talk to regarding appropriate unreimbursed medical expenses or a list of those expenses and how to include that in the contract etc... Any words of advice would be awesome.