You have not copied a spell using Chandra's ability this turn.
Steps
Activate Vampire Hexmage by sacrificing it, removing all counters from Invasion of Arcavios.
Invasion of Arcavios triggers, causing you to exile it and cast it as Invocation of the Founders.
Activate Chandra's first ability by putting a loyalty counter on it, adding ({1} magic symbol) ({W} magic symbol) .
Cast Flicker by paying ({1} magic symbol) ({W} magic symbol) , targeting Invocation of the Founders.
Chandra and Invocation of the Founders trigger, copying Flicker twice, with one copy targeting Chandra and the other targeting Sister Hospitaller.
Resolve the first Flicker copy, blinking Chandra.
Resolve the second Flicker copy, blinking Sister Hospitaller.
When Sister Hospitaller enters the battlefield, it triggers, returning Vampire Hexmage to the battlefield from your graveyard and causing you to gain 2 life.
Resolve the original Flicker, blinking Invocation of the Founders, causing it to enter the battlefield as Invasion of Arcavios.
When Invasion of Arcavios enters the battlefield, it triggers, returning Flicker to your hand from your graveyard.