Johnny , i would still prepare some milk ready, let the jill keep them warm & mother them, i had a similar problem some years ago, i let the foster jill do the mothering, but still fed them by hand , these kits were around 4 weeks old though & were chomping on meat as well .
To be honest all you can do is try , if she has no milk you will have to carry on with the supplimentry feeds if they have a chance of surviving.
Other thing to watch is the foster jill , if she is still producing milk she may well end up with milk fever something else i have experienced when they give ther