Praise be to Allah.
There is nothing wrong with that, because this comes under the heading of gifts and does not come under the heading of transactions. So if she gives them something and they accept it and keep it, then they have the choice: if they wish, they may give her something and if they wish they do not have to give her anything; if they wish they may give less or more than that.
So long as there are no stipulations between them and there is no transaction – rather each of them gives the others what she chooses and wants to give them– then this is permissible and there is nothing wrong with it. And Allah knows best.
Fataawa Samaahat ash-Shaykh ‘Abdullah ibn Humayd (may Allah have mercy on him), p. 22.