Look at the facts: 1) the DS will kill anyone in PDJT family given the chance, 2) Ivana was very much into her looks and body and kept herself in good shape, 3) the house had 7 floors and a People article quotes her as saying she always takes the stairs and 4) rich people have the access to the best preventative healthcare - chances are low that she had a medical event which caused the fall.

Also worth noting that people do die from falls frequently. In fact, I think it is one of the leading causes of death.