Should I owe mother for financial help?

My mother helped me financially at a devastating time in my life when I was dealing with a mentally ill husband and having trouble making ends meet. Now years later my older adult sister is the executor of my mother's will (mother has some dementia) and found the old paperwork that had records of money given to me. She insisted to the lawyer that it be put into the will & trust as a loan so that it would later be taken out of my third (there are 3 siblings). Our mother said no to that with the lawyer present but now I am so hurt and distrustful of that sister that I don't want to see her. I feel like I've been stabbed in the back. She has always had plenty of security and money with her husband and has never had to work. I just can't understand how she could be so uncaring and hurtful. I thought we had a caring relationship. What would one say to a sister like that? I've already told her the whole financial story of my income, etc. and she acts indifferent. If I was made to relinquish that part of the one-third it would cause tremedous hardship later.