I'm going to scream. She isn't a foster child. Charlie is her guardian.
I totally agree with you on that one. It seems that they have toned down the whole Charlie/Ruby thing, especially with only a brief mention from Charlie about her 16 year old daughter being trapped inside a burning building surrounded by rioters. If we don't see some interaction between them, and Ruby (who after all only is 16) moving back in with Charlie , I think we can conclude that there probably won't be any "real" mother/daughter relationship between them.