Why was Accolon killed by Morgan Le Fay?

In the book, L'morte de arther, he was her lover. She gave him the sWord excaliber after giving arther a false one. She told him to use it in his next battle which was a stranger. The stranger though was arther in disguise so accolon dind't know he was fighting arther. He broke arther's fake sWord but arther kept fighting him and wounded him. Accolon then bled out when they reached a town, but arther was saved in time. When she found out accolon was killed (she set it up so he would accidently kill arther) she got all angry and sad. So I dn't think she meant for him to die.