Ask. There are certain conditions like endometriosis which do have a genetic correlation and do affect fertility, but they are halachically required to tell you the truth about it. If the mother and aunt has it, but the daughter doesn’t, there shouldn’t be any issues. If the daughter does have it, it is a concern.
OTOH, I know a person who was at high risk for fertility issues, and so far has 9 children Ka”h. Hashem runs the world.