I admit I don't know very much about fostering but if the child had to be placed with foster parents in the first place, why is the natural mother having any say in what happens? Surely children are only put up for fostering if the mother is somehow incapable of looking after the child herself.
BTW, be careful of placing such a high emphasis on 'respecting people's religious beliefs' when there are children concerned. It's all well and good people being able to worship freely, but using that religious belief as the basis for making decisions concerning a child leads down some very dangerous paths...
Kids are fostered for all sorts of different reasons and fostering is rarely a permanent solution. To deny the natural parents any say in how the child is brought up, when in most cases the child will be returning home, is ridiculous.
Making uninformed judgements about the natural parents of fostered children is far more dangerous than respecting peoples basic human rights.