She probably just hasn't bothered with dealing with her cousin on top of probably not having seen Nera to notice she's done something about her eyes to decieve the other family into adopting her.
Everyone falls in love with her and she creates a harem and they all live happily ever after realising that monogamy/monoandry is just too overrated. Even the cat in the bag believes it and joins the harem.
Didn't expect there to be 10!