OK,
Annabella Selina Gardiner is my second great grandmother's husband's sister's husband's wife.
Howard Rickman → Wayne Owen Rickman your father → Owen Percy Rickman
his father → Hazel Maud Rickman (Boone)his mother → Maud Mitchell (Tipper)
her mother → Henry Mitchell her husband → Mary Ann Mitchell his sister → Alexander Martin her husband → Annabella Selina Gardiner his wife