Spoiler alert
Vintner is suppose to bring her at the coming of age ball but Eclise brings her to the estate before that. Eclise gets to the point that he so obsess with Penelope that he wants to become the only person Penelope can rely on. He knew that with the real daughter present they were going to toss Penelope aside. Penelope attempts to kill herself at the coming of age ball because she believes she has lost the game.

for those who read the SPOILER! (maybe)
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when she said “don’t betray me eclis” fricken cried. ╥﹏╥