I lend $450,000 to my brother with 10% intrest and he passed away 2 yrs ago,and I paid for his and his son''s funeral expenses also ($48,000).and

I collected a promisory note from sister $450,000+48,000+ the 10% intrest together $575,000.after that I lend another $350,000 to my sister in law ( i have promisory note for $350,000 also) she paid me back $450,000.she is claiming that she dont owe anything to me now because she borrowed from me 350,000 + the funeral 48,000 and she is telling that she over paid me 50,000.which is better way to make a claim,agaist her or estate? she dont have anything under her name but eveything under the estate and corporations.and assessed the estate very below the market value and all the propertys have enough debt.she have 2 good property''s under some corporations worth 10 million and those property''s are paid off.she paid off the property''s with my brother''s life ins money.please advice.