The protagonist Sarah should not have to worry about inbreeding affecting her children.
According to the answer of fraxinus a parent and child share 50 percent of their genes, and a grandparent and grandchild share 25 percent of their genes.
Extrapolating, a great grandparent and great grandchild share 12.5 percent of their genes, a great great grandparent and great great grandchild share 6.25 percent of their genes, a great great great grandparent and great great great grandchild share 3.125 percent of their genes, a great great great great grandparent and great great great great grandchild share 1.5625 percent of their genes, a great great great great great grandparent and great great great great great grandchild share 0.78125 percent of their genes, and so on.
An ancestor of Sarah born 5,000 years before Sarah would would probably be her ancestor about 200 generations earlier, so they should certainly not share any more genes, including the harmful recessive genes that make inbreeding dangerous, than any two randomly selected persons.
Of course Sarah might travel 5,000 years in the past and find some outstanding person to marry, not knowing that he is another time traveler and in fact Sarah's long lost brother who was separated from her when they were very young.
I note that if Sarah travels back in time about 5,000 years from the present time about AD 2023, she will appear in about 3000 BC. And about 3000 BC was about the beginning of recorded history in Mesopotamia and Egypt, and generations, centuries, or millennia, before the dawn of recorded history in other regions. So if Sarah travels back in time from AD 2023 she will might meet the earliest historical persons in Egypt or Mesopotamia, or might appear in a prehistoric - because preliterate - society elsewhere in the world.
Of course time travel is almost certainly impossible, and if possible almost certainly impractical. So if scientific advances ever permit practical time travel, it might be tens or hundreds of thousands or millions of years in the future. So it is perfectly possible that Sarah might travel 5,000 years into her past and arrive many thousands of years in our future.
And if Sarah travels from some time in our future 5,000 years into her past, she might take many future inventions along with her which might make her seem like a god to the people in her past, especially if her past is also far in our past when technology was less advanced.
Another reason why Sarah shouldn't worry about possible inbreeding of her children is that she is going to take billions of bacteria, viruses, etc. with her into the past. And they well introduce modern genes into the gene pools of thousands of different species of microscopic life. This will change the evolution of new species of microbes out of the past species of microbes.
Some species that produce deadly diseases in humans will not evolve, and so many humans will live who would have died, and some will marry people who otherwise would have become ancestors of Sarah.
And some species will evolve that cause deadly diseases in humans which never evolved in Sarah's timeline, and they will kill many people who would have lived longer in Sarah's timeline, including many who would have later become ancestors of Sarah.
So many of Sarah's ancestor's would never have been born, and so Sarah would never have been born. So if Sarah travels back in time she will certainly prevent herself from ever being born, and so won't have to worry about the possible genetic problems of her children.
Unless Sarah has found a a way to avoid being erased by changing history, she won't have to worry about her children having genetic defects because she will prevent herself from ever being born and so won't travel into the past to have any children.
Of course most time travel stories ignore the reasons why it would be totally impossible for a time traveler to avoid preventing their own birth. So you might just want to avoid all discussion of grandfather paradoxes and how Sarah avoids them.