Complex sentence: McCready is the third cast member from this season to die, and the fifth cast member from the series overall to die within a two year period, though her death is the first of which a cast member's addiction was not contributing factor to their death.
Split into simpler sentences: McCready is the third cast member from this season to die, and the fifth cast member from the series overall to die within a two year period. However, McCready's death is the first of which a cast member's addiction was not contributing factor to their death.