So apart from talking to her and explaining that it is all in good faith etc etc, what else can i do to make her secure?
If it is being said in front of you. Just tell those aunties and uncles that . Naaa you love both of your girls and would never give any of them away , not for a million , billion dollar , never ever.
This is the only thing she will understand that parents will never let anything like that happen.
Once in a while I would like a cute kid and I will tell that kid directly " Can I adopt you" or to their parents "can I adopt your kid"
It does not sound as bad as taking them away.