Parents help - What would you do if your 3 year old was being bullied?

i had the kinda same situation my daughter is 3 1/2 almost 4 and the other little girl 4 almost 5 she lives by us and the one day she came over and wanted to play with my daughter however my daughter was on the computer and knows that when she is on it she cant have friends over so she told the other little girl i don't want to play today i want to play my game (my daughter is around kids all day at daycare) and the little got all rude and was like i will never play with you again and i am never coming here again and my daughter at first was like fine didn't care (the other girl gets bossy and snotty all the time) so the little girl left 10 minutes later the little girl is back on my daughter repeated that she didn't want to play and the other little girl snapped at her talking about i don't like you and i hate you and i am never playing with you again the mom was standing in the hall and i heard it all got the little girl and took her home and disciplined her and the next time the little girl came down i turned her away and explained why i did that, these two also play with a another neighbor girl who is older and sometimes times when they get to together my daughter gets left out till the older one is gone and i talked to them about and the parents and said i will not tolerate this and it didn't change so i stopped playing together for a while and then they get a long fine every once in a while i can see it starting to start up and i just say if you all cant get along then no more playing together and being i have done it before they no i will do