"I am not your friend anymore."
Translation:אני לא חבר שלךָ יותר!
The words חבר and ידיד can be different in two ways. Either חבר as a close friend and ידיד as a casual friend, but we don't use ידיד in this sense anymore in modern conversational Hebrew. Or חבר as someone you date and ידיד as "just a friend".
You can. But maybe you wrote it in the wrong location? The correct answer should be:
אני כבר לא חבר שלך