advice needed

Need some advice I had a messy break up with a friend that was very close to my 4yr old well we saw each other today and my 4yr old had a complete melt down as she wanted to go with her. She does not understand that mummy and this person are no longer friends. I dont know what to do or how to deal with this. We no longer want to bw friends there has been far too much water under the bridge for that so should I just tell my daughter this. We will see each other from time time and we cant avoid it.