Try gradually increasing the distance you throw her toy...build up from the 4ft she currently has as her 'limit'.
I agree with snooks to make the 'game' more exciting for her, and to reinforce to her that bringing the toy to you is great! Perhaps increasing the value of the reward when she brings you her toy would help? Also you could try ignoring her when she doesn't fetch the toy, perhaps keep looking at the toy and slowly walk towards it, then when she brings it give her heaps of praise...sounds like lots of interaction with you would work well for you as a form of praise for her?