My mother passed 5 years ago and left a home which 3 of My sisters share. One sister moved out without giving notice. Can we legally change the lock

No.  She is a part owner.  Hopefully you have settled our mother's estate and, whether there was a Will leaving each of you 1/3rd or you each inherited 1/3rd under the laws of intestacy, have recorded an Executor's or Distribution Deed in all three names.