She also was something like 7/8 white and looked just like Martha Jefferson’s twin.
During my time a The University, it was said that Mr. Jefferson transferred his love from his deceased wife, Martha, to Sally.
Also, Martha Randolph Jefferson, Mr. Jefferson’s daughter, acted as First Lady during his service as POTUS, so Ivanka’s role has historic precedent.
Thanks
There have been several other Presidents for whom a female relative, rather than a wife, filled this role.