this's my theory and it might be spoiler but...
knowing that rourou's a heir for feng family and the new baby's (maybe) a heir for yi family. if the aunt end up with yi's baby she still end up with rich baby but she can't claim the inheritance since it's a different family. if the truth unfold and it's really yi's baby the aunt only have two choice which let the bay back to yi or end up with nothing, the worst possible way is using the baby as a threat or bribe but she still get sued. if it's feng's baby(which i am sure it's not since rourou already has the birthmark so rourou's feng family's heir) she still can claim the inheritance but she will need to never unfold the fact that it's feng's baby. if it's feng's she will still get the money as long as the baby has the mark(which impossible since rourou already has it) as the first next generation heir of the family even without unfold the truth. But lol aunty dont know that there's already another next generation heir (rourou) and grandpa and greatgranpa already acknowledge him. she still get the chance to get all the inheritance even after she know the truth that there's rourou but she need to kill rourou first and that will be pretty hard and i guess the aunt's not that patient. she will end up using the baby as a threat or just reveal it when they're bickering before she get the money lol, we know how the greedy will end up at the end, either it's jail or hell.
if my sister going through hell to fix our family of course i will worship her, good job boy!