I guess the question is genetics...are there diseases that could erupt or things like diabetes that are considered inherited...so if she dies ....who would be able to explain it if the husband does not know. Doesn’t the child need to know eventually who their real father is?
Telling the husband now is cruel. It has nothing to do with him. She and the ‘friend’ can carry that guilt. That is their penance.
Having raised two step children from toddlers, the answer is she already knows who her "father" is...
The one who loves her today, tomorrow and forever unless that love is tested by a remorseful wife..
A second more important point does her "real father" even know she is his...
What if he rejects his daughter, after all he had no problem banging his best friends wife !!!
I guess the question is genetics
Pretty low chances of that being a problem...
All in all, as they say "let sleeping dogs lay"